Wheat Belly: Fat or Flat

Does a diet high in refined wheat bread make people hungry, fat, diabetic, and prone to cardiovascular disease, as claimed by some authors?

In 1979, Mickelsen et al (full text here ) wanted to see if people can eat a diet high in regular refined wheat bread and lose body fat.  Their rationale follows:

This paragraph seems to fit our times though written more than 30 years ago:

"Incorrect assumptions have taught that bread should be eliminated from weight control plans; this idea has been fostered by the recommendations and instructions of many weight-reducing plans (2).  The instructions of many fad-type diets state that 'starchy' foods such as bread and potatoes should be avoided...Measurement of food intake and caloric deposition in the carcasses of rats fed a high-fat or a natural grain diet indicated that for each 1000 cal intake the high-fat fed rats retained twice as many calories as the grain-fed animals (3)."

To find out if a diet high in wheat grain would have the same effect on humans as on rats (reduced caloric retention), Mickelsen et al recruited 16 overweight college males, all of whom wanted to lose between 4.5 and 12 kg (10 to 26 pounds).

The subjects all agreed to eat all meals in a cafeteria, avoid alcoholic beverages, and consume 12 slices of wheat bread every day (four slices at each of three meals) for eight weeks.  Mickelsen et al randomized the subjects into two groups, one of which received high fiber bread and the other received white bread (i.e. made from refined wheat).  All subjects “were instructed that to lose weight, they would have to restrict caloric intake” but they were allowed to eat as much as desired at meals and were also allowed to snack between meals as desired. 

 

The two types of bread differed in several respects.  The high fiber bread supplied 50 calories and two grams of fiber per slice, while the regular bread supplied 70 calories and only one-tenth of a gram of fiber (the high fiber bread had 20 times the fiber of the regular bread).  The high fiber bread had about half as much fat and twenty-five percent less digestible carbohydrate than the regular bread. The high fiber bread had about 50 percent more iron, present in the added fiber, and was enriched with calcium because the researchers anticipated that the high fiber bread would reduce calcium absorption, although it turned out that the higher fiber intake did not reduce calcium absorption.

Thus, each day of the study period, those eating the high fiber bread ingested 600 calories and 108 g carbohydrate from wheat bread, and those eating the regular bread ingested 840 calories and 156 g carbohydrate from wheat bread. 

For comparison, Ezekiel Bread, a favorite of Ripped author Clarence Bass, supplies 11 g of digestible carbohydrate, 3 g of fiber,  4 g of protein, and 65 calories per slice (the label lists 80 calories per slice but that was derived by including the potential caloric value of the indigestible fiber, which is unavailable to us).  A loaf of Ezekiel Bread has 20 slices, so the subjects of this study ate more than half a loaf of bread every day.  Twelve slices of Ezekiel Bread supplies only about 780 calories, about half of the 1500 calorie intake that would produce weight loss in many women.

So did eating all this wheat make their bellies fatter, or flatter?

Over the eight week period, the subjects eating the regular bread lost an average of 6.25 kg (about 14 pounds; range 4.2 to 7.3 kg), while the subjects eating the high fiber bread lost an average of 8.77 kg (about 19 pounds; range 6.2 to 11.4 kg).  Thus, those eating 12 slices of white bread daily lost an average of one and three-quarters pounds of body weight each week; and those eating 12 slices of high fiber daily lost an average of two and two-fifths pounds of body weight each week.  They did not make any changes in activity level.

Of interest, the subjects succeeded in reducing their caloric intake by 25 to 38 percent while simultaneously experiencing a decrease in hunger.   At the end of the study, the subjects consuming the high fiber bread reported that they did not feel hungry at any time.  Two of the subjects eating the regular bread did feel hungry at the end of the study, one of those only before meals.

The group eating the regular bread had a decrease in serum cholesterol from 231 to 155 mg/dL,  and the group eating the high fiber bread decreased serum cholesterol from 224 to 172 mg/dL.

Follow-ups on 9 of the participants at 3 months, 6 months, and 9 months found that those four who stopped eating the bread regained the weight they had lost, while those five who continued to eat the bread (regular, higher calorie) either maintained most of their weight loss or lost even more weight.

Summary

In summary, this study found that all participants reduced their hunger, cholesterol levels, and body weight by deliberately consuming a dozen slices of bread each day, four slices at each of three meals, more than half a loaf of bread daily, regardless of whether the bread was high in fiber or made from refined white flour.   Those who abandoned this regimen gained the weight back and those who continued to eat a diet revolving around refined white bread maintained their weight loss or lost even more weight. 

Eating 12 slices of wheat bread did not

• increase their hunger (it decreased their hunger)
• increase body weight (it resulted in weight loss by reducing other food intake)
• increase their blood sugar levels (they had no change in blood sugar levels)
• raise the risk of heart disease (it decreased the levels of a major heart disease risk factor, total serum cholesterol)

All this without inducing the headaches, nausea, malaise, fatigue, and constipation that commonly affect people, particularly women, when consuming high-fat, low-carbohydrate diets.

This study using Caucasian subjects resonates with the experience of millions of Asians who eat an average of one pound of dry rice daily and maintain low body fat levels throughout their lifespan. 

Source:  Abdullah et al (full text pdf)

Effect of dietary fat on satiation within and between meals

Blundell et al performed a series of four experiments to determine the effect of fat content of a meal on satiety, both during and after meals. [1 full text ]

The first  experiment involved giving 16 lean, healthy subjects a standard breakfast of 440 kcal, or the same breakfast supplemented with either fat or carbohydrate calculated to provide ~360 kcal.  The standard breakfast consisted of orange juice, scones, and fruit yogurt.  The supplements consisted of either polyunsaturated margarine and cream, or a combination of sucrose, maltodextrin, and glucose.  The following table provides the data on the three types of breakfasts:

Each individual tested each breakfast with a one week interval between tests.  The subjects rated the palatability of the meals, and rated hunger, desire to eat, fullness, and prospective consumption before the breakfasts and periodically during the rest of the day.

After the breakfasts, the subjects ate measured meals, provided by the experimenters, for lunch and dinner on the same day, and kept weighed food records for the period between dinner that day and breakfast the next.

In this experiment, neither the high fat nor the high carbohydrate breakfasts appeared to exert any significant effect on intakes of macronutrients at the subsequent lunch or dinner.  However, subjective reports of hunger did differ between the high carbohydrate and high fat meals.   Specifically, the subjects reported less hunger with the carbohydrate-supplemented meal compared to the baseline or fat-supplemented breakfasts.  The following figure depicts the effects:

When the subjects ate the carbohydrate-enriched breakfast, they experienced less post-meal hunger than when given the fat-enriched breakfast, indicating that they found fat less satisfying than carbohydrate during the post-ingestive phase. 

In the second experiment, 12 lean healthy individuals consumed the same breakfasts given in experiment one, followed by a snack provided 90 minutes after the breakfasts.  Subjects rated themselves as less hungry and more full after the carbohydrate-enriched breakfasts, compared to the fat-enriched breakfasts.   They also ate smaller snacks at the 90 minute mark when they had the carbohydrate-enriched breakfast, compared to when they ate the fat-enriched breakfast.  The following figure depicts the effects:

In the third experiment, 16 lean healthy subjects consumed the same breakfasts as in experiment one, followed by a snack 90 minutes after the breakfast, or a meal 270 minutes after the breakfast.   The following table depicts the results:

When given the carbohydrate-enriched breakfast, the subjects  voluntarily ate a smaller snack at 90 minutes after, compared to what they ate after the fat-enriched breakfast.  Of interest, although the fat-enriched breakfast supplied ~800 kcal, 90 minutes after that breakfast they voluntarily consumed a snack the same size as they had 90 minutes after the 440 kcal baseline breakfast.  This means that at 90 minutes after the breakfast, the 800 kcal breakfast providing 57% energy from fat was no more satisfying than the 440 kcal breakfast providing only 10% energy from fat.  

The greater satiating effect of the high carbohydrate breakfast disappeared at 270 minutes.  Blundell et al attributed the greater satiating effect of the carbohydrate-supplemented breakfast at 90 minutes to the greater elevation of blood glucose achieved by the carbohydrate-rich breakfast.  As the glucose was oxidized or stored over the next 180 minutes, this satiating power declined.

In the fourth experiment, 12 obese women ate either one of two lunches, each on two different occasions.  One lunch supplied 527 kcal, the other supplied 985 kcal.  Between lunch and dinner, the subjects rated their hunger at one hour intervals.  At dinner, each woman was offered either foods supplying 50% of energy as fat, or 50% of energy as carbohydrate and allowed to eat as much as desired.  So, each woman had four different procedures:

1.  A 527 kcal lunch, followed by an ad libitum high-fat, low-carbohydrate (50% energy as fat) meal for dinner.

2.  A 527 kcal lunch, followed by an ad libitum low-fat, high-carbohydrate (50% energy as carbohydrate) meal for dinner.

3.  A 985 kcal lunch, followed by an ad libitum high-fat, low-carbohydrate (50% energy as fat) meal for dinner.

4. A 985 kcal lunch, followed by an ad libitum low-fat, high-carbohydrate (50% energy as carbohydrate) meal for dinner.

Not surprisingly, the size of the mid-day meal determined the course of subjective hunger during the afternoon, i.e. the smaller meal was followed by earlier return and greater intensity of hunger as depicted in the following figure:

However, the size of the midday meal did not affect the energy content of the ad libitum dinner meal as much as the relative fat and carbohydrate contents of the offered dinners.  The following table displays the impact of midday meal size and dinner composition on satiation during the dinner meal:

Regardless of whether given the high-energy or low-energy midday meal, the subjects consumed an average of 5.6 MJ/1336 kcal for dinner when given high-fat foods, but only 2.8MJ/677 kcal when given the high-carbohydrate/low-fat foods.  This demonstrated that within a meal, high-carbohydrate foods appear to have a greater satiating effect, i.e. subjects voluntarily consumed less food energy when given a high-carbohydrate selection compared to when given a high-fat selection.

Since the high-fat meal was at least 50% energy from fat, and the average intake was 1336 kcal, this means the average intake of non-fat nutrients at the high-fat meals was at most 668 kcal, approximately the same as the 677 kcal the women consumed when eating the low-fat high-carbohydrate meals. It appears as if the women were eating to achieve a certain intake of non-fat nutrients (carbohydrate or protein), regardless of the fat content of the food.  Since the high-carbohydrate meals supplied more carbohydrate and protein per ingested gram of food, the apparent carbohydrate or protein drive was satisfied with less total fat and energy intake.

The researchers followed the food intake of these women after dinner and throughout the next day as well.  Some would predict that the high fat intake of the high-fat meal would reduce post-meal and next-day food intake.  That did not happen.

 The women consumed after-dinner snacks averaging 310 kcal after the high-fat meal, and 391 kcal after the low-fat, high-carbohydrate meal.   The 81 kcal lower energy intake is insignificant compared to the nearly 700 kcal greater kcal intake at the preceding high- meal. 

The day after having the high-fat dinner, the women consumed an average of 1800 kcal, whereas the day after having the low-fat dinner, the women consumed an average of 1556 kcal.  This ~250 kcal difference did not reach statistical significance, but the direction was opposite of the prediction that they would compensate for the high-energy intake of the previous day by reducing energy intake in subsequent days.  It may even suggest that the high-carbohydrate dinner had a satiating effect that lasted into the next day. 

Now, looking at this from an evolutionary perspective:  If humans find carbohydrate more satisfying than fat, this suggests that evolutionary diets were high in carbohydrate and low in fat.  An organism geared to consuming fat would get the most satisfaction from fat.  An organism geared to consuming carbohydrate would continue eating until it either satisfied its carbohydrate requirement, or reached the limit of  its ability to convert protein or glycerol to carbohydrate, whichever comes first, regardless of “energy” intake--exactly as seen in these women. 

Since the brain regulates eating behavior and it primarily relies on glucose as its main fuel, we can reasonably expect that the brain has a carbohydrate drive, meaning that it drives people to eat until they ingest adequate glucose, or enough protein to provide the brain with adequate glucose.   

In other words, I would predict that, barring interference from the conscious mind (i.e. so-called "discipline") attempting to control macronutrient ingestion,  hungry people will keep eating until they at least minimally satisfy their carbohydrate requirements either directly from dietary carbohydrate, or indirectly from dietary protein, or until in the latter case they reach the limit the body imposes on protein ingestion, whichever comes first, regardless of total fat (or energy) intake.

Several studies appear to indicate that primitive Eskimo diets aligned with this prediction.  Several studies have indicated that Eskimos consume  very high percentage of energy as protein [Table from 2 full text ]:

On average these studies suggest that free living Eskimos derive 48% of energy from protein.  Assuming a 3000 kcal diet for an active male, this would be 1440 kcal/360 g of protein daily.  Since the human protein (70 kg reference man) requirement ranges from 50 to 75 g per day under most circumstances, these data indicate that the Eskimo may consume ~300 g excess protein daily.  According to Jungas et al, about 58% of catabolized protein will appear in the blood stream as glucose [3 ] .  Therefore, an Eskimo consuming about 300 g excess protein daily will generate from this about 174 g glucose, approximately the minimal amount required by the central nervous system. 

Some have criticized the data in the table above claiming that Eskimos eat ~80% of kcalories as fat based on claims made by Stefansson.  I find it extremely unlikely that four separate investigations produced incorrect data on Eskimo macronutrient consumption, and since Stefansson did not directly measure the macronutrient intake of Eskimos, I see no reason we should accept his estimate as more accurate.

The idea that Eskimos couldn’t have eaten a diet providing 48% of energy as protein is based on the claim that a protein intake of this magnitude will lead to so-called “rabbit starvation” from excess protein intake.  About “rabbit starvation” Cordain et al [4 ] have written:

“Excess consumption of dietary protein from the lean meats of wild animals leads to a condition referred to by early American explorers as “rabbit starvation,” which initially results in nausea, then diarrhea, and then death (39). Clinical documentation of this syndrome is virtually nonexistent, except for a single case study (42). Despite the paucity of clinical data, it is quite likely that the symptoms of rabbit starvation result primarily from the finite ability of the liver to up-regulate enzymes necessary for urea synthesis in the face of increasing dietary protein intake.” [Emphasis added]

Aside from the fact that clinical documentation of “rabbit starvation” is “virtually nonexistent,” Shaefer reported that primitive Eskimos on native diets had enlarged livers in comparison to Caucasians, and when they reduced protein intake, substituting carbohydrate, their livers reduced in size [5, full reference below].  This may suggest that Eskimos on native diets had livers adapted to chronically very high protein intakes via hypertrophy, whereas explorers (including Stefansson) may have experienced acute “rabbit starvation” when forced to eat very lean meat because unlike Eskimos they did not have previous lifelong exposure and hepatic adaptation to very high protein intakes.  

A Word About Protein And Satiety

A number of studies have shown that when given energy-restricted diets, people find higher protein intakes more satiating (within meals) and satisfying  (between meals) than lower protein diets.  For a while I felt impressed by this, thinking that protein is more satiating than any other nutrient. 

However, I now think this finding simply reflects the long-known fact that when when we restrict total food energy intake, and therefore carbohydrate intake, protein requirements increase, because carbohydrate restriction increases the use of lean mass to produce glucose.  Thus, under hypocaloric conditions, a drive to meet increased protein requirements--what we might call "protein hunger"-- may surface. 

Again, it has been known for a long time that protein requirements increase under hypocaloric conditions, so these recent studies showing higher protein diets to be more satiating under hypocaloric conditions appear to me to just be late application of something we have known for decades.  These findings do not mean that protein is the most satiating nutrient under all conditions.  I performed a quick PubMed search for studies of the satiating effects of protein under ad libitum conditions, and found only one study  [6 abstract ] which reported both "higher protein led to greater daily fullness" and "Protein quantity did not influence daily hunger, glucose, or insulin concentrations," i.e. inconsistent effects.


Given what we know about the satiating power of carbohydrate and protein, and fat balance versus energy balance, Astrup suggests that the optimal diet for reducing body fat might be very low in fat, high in carbohydrate, and moderately high in protein, for example 60-65/20-25/15 carbohydrate/protein/fat [7 abstract, 8 full text].

Take Home

1)  This series of clinical studies found that both lean and obese people not invested in consciously controlling their macronutrient intakes experienced most satisfaction and less hunger from high-carbohydrate than from high-fat meals.

2) The biological basis for this probably lies in the brain's demand for glucose.  The brain drives eating behavior, and since it prefers glucose to other fuels, it has a drive to satisfy its own requirement for glucose.

3)  Barring conscious control of macronutrient intake/ratios, a majority of people probably will eat to achieve an adequate intake of carbohydrate, either by consuming carbohydrate directly, or by consuming enough protein to produce adequate carbohydrate, continuing to eat until either they satisfy their carbohydrate drive, or they meet the limit of the body's ability to convert protein to carbohydrate, whichever comes first, and regardless of total energy intake. 

4) If people choose high-fat foods to satisfy carbohydrate requirements, they will very likely consume more fat (grams) than they can burn in a day, leading to progressive gain of fat weight.

Notes:

5. Schaefer O. Eskimos (Inuit). In: Burkitt DP, Trowell HC, eds. Western Diseases: Their Emergence and Prevention. Cambridge, MA:  Harvard University Press, 1981:114.

Fat balance versus energy balance

When losing “weight,” you want a selective process.  You want to lose fat, not essential lean mass, which includes essential water (i.e. not water of edema), muscle, organs, and glycogen.

When a person adopts a low carbohydrate diet, the body continues for several days to draw down glycogen stores to fuel the brain and muscles.  Glycogen stores typically amount to about 300 to 400 g in the average subject, 100 g of which can reside in the liver. The body stores glycogen in combination with water in a ratio of about 3 g water for each 1 g of glycogen.  Thus, on a low carbohydrate diet, initial depletion of glycogen can alone account for up to 1.2 to 1.5 kg, creating an illusion of rapid change in body composition.

As noted by Flatt,  “The body ignores that 1 g of fat contains more than twice the energy present in 1 g of carbohydrate, an element of information needed to determine the energy balance.”(1) The body does not regulate energy balance; it regulates the balances of carbohydrate, protein, and fat, each of which has its own economy.

Ingested carbohydrate, protein, and fat differ markedly in their potential fates:

Carbohydrate	Protein	Fat
Utilization in structures of glycomolecules	Utilization for repair and maintenance of tissues	Utilization for repair and maintenance of cells
Oxidation to support body functions	Conversion to glucose; oxidation to support body functions (only in a carbohydrate deficient system)	Oxidation to support body functions
Oxidation to produce heat	Conversion to glucose; oxidation to produce heat (only in a carbohydrate deficient system)	Storage as body fat
Storage as glycogen (500 to 600 g)	Conversion to glucose; storage as glycogen (only in a carbohydrate deficient system)
Conversion to body fat	Conversion to body fat

Numerous studies have shown that the concept of energy balance does not strictly apply to human metabolism because of the different ways the body manages the separate economies of  fat, protein, and carbohydrate.  

As an example, Miller and Mumford did three experiments involving overfeeding humans with a supplement of 1300-1500 kcal per day, either high in protein (~15%) or low in protein (~2.7%). [2 full text]   Fat content of high- and low- protein diets was held constant, so high protein diets were reduced in carbohydrate, and vice versa. 

Their data showed large deviations from predictions of the energy balance hypothesis.  Subjects overfed a low-protein, high-carbohydrate diet consistently gained less weight than predicted by the increased kcaloric intake; in fact, some subjects on low protein diets lost weight despite consuming an excess of 8-10,000 kcal in a week. 

In one experiment, subjects on low protein diets overconsumed an average of 35, 230 kcal but gained only 0.9 kg, compared to the energy balance prediction of  5.9 kg. In contrast, subjects getting the excess kcalories from higher protein foods gained an average of 3.7 kg, two-thirds of the amount predicted by the energy balance equation.  Miller and Mumford ruled out significant loss of lean mass by multiple methods of estimating body composition, including whole body potassium, skinfold, nitrogen balance, and urinary creatinine, none of which indicated significant change in lean body mass in these subjects.

These data indicated that, given the same excess “energy” intake,  higher protein intake increases body weight gain compared to higher carbohydrate intake. These data clearly contradict the energy balance idea as well as the idea that high protein diets have a metabolic advantage over high carbohydrate diets; on the contrary, they suggest that high carbohydrate diets have the metabolic advantage. 

Prewitt et al [3 full text] found that women (black, Hispanic, white, and Asian) assigned to a 60% carbohydrate, 20% fat diet required 14-28% (average 19%) higher caloric intake to maintain weight than when assigned to a 44% carbohydrate, 37% fat diet (protein intake was constant at ~19%).  Despite efforts to maintain stable body weight on the lower fat intake by increasing carbohydrate intake,  the subjects lost an average of 11% of body fat (2.5 kg) over 24 weeks. 

Grams, Not Calories

In the nutritional biochemistry literature, research along these lines has led to the realization that the body deals with substrate balances, not energy balance.   That means, the body has a fat balance, protein balance, and carbohydrate balance, the latter two of which it appears to regulate. 

Since the body processes each nutrient (protein, fat, carbohydrate) differently, we can’t reduce them to hypothetically equivalent kcalories with equivalent fates.  Ironically, this has become the battle cry of advocates of low carbohydrate diets, when the data (some of which I cited above, some below) overwhelmingly supports the conclusion that high carbohydrate diets have the “metabolic advantage” over low carbohydrate diets.

To lose body fat, you must create a metabolic situation in which the body oxidizes more fat than it deposits in stores, which we can call ‘negative fat balance.’  This could occur through increased oxidation of fat relative to deposition, or decreased deposition relative to oxidation, or both. 

 

Hill et al tested nutrient balance in humans using diets high and low in carbohydrate or fat. [5] Figure 2 shows the nutrient oxidation rates for protein, fat, and carbohydrate at baseline, and three different experimental diets.  The high fat diet supplied 20 percent of calories from each protein and carbohydrate, and 60 percent from fat.  The high carb diet supplied 20 percent of calories from each protein and fat, and 60 percent from carbohydrate.  The mixed diet supplied 20 percent of calories as protein, 35 percent as carbohydrate, and 45 percent as fat. 

Click for larger version

As shown, on the high fat and “mixed” diets, the subjects oxidized (“burned”) more fat than either carbohydrate or protein, and on the high carbohydrate diet, they oxidized more carbohydrate than either fat or protein.  Notice that protein oxidation was essentially the same regardless of diet, because all diets had equivalent proportion of protein.  This confirmed the long-known fact that carbohydrate spares fat oxidation.  From this figure, you might naturally conclude that eating a low carbohydrate diet will lead to fat loss by increasing fat oxidation.

The next figure shows the balance (intake minus oxidation) of protein, fat, and carbohydrate on each of the diets.

Click for larger version

On the 60% fat diet, the subjects were in slight negative fat balance (burning more fat than consumed) on day three, but by day seven, they were in positive fat balance (burning less fat than consumed)--hence, on day seven they were storing dietary fat in adipose.  This happened despite the fact that they had increased fat oxidation.  Decreasing dietary carbohydrate forced the body to burn more fat, but because they were consuming a high fat diet, they were consuming more fat than they could burn in a day, resulting in a positive fat balance....increasing adipose.

In contrast, the subjects on the 45% fat and 20% fat diets were in negative fat balance—burning more fat than consumed—on all measured days, with those on the 20% fat diets in the greatest negative fat balance—losing body fat at the greatest rate.

Note that this means that on the same kcaloric intake, when the subjects ate a 60% fat diet, they were accumulating body fat, but when they ate a 45% or 20% fat diet,  they were losing body fat...and they lost fat faster on the 20% fat diet than on the 45% fat diet.

Notice also that when the subjects were on the 60% carbohydrate diet they had positive protein balance at both measured days, but when on either the 60% or 45% fat diets, by day seven they were in slight negative protein balance—burning more protein than consumed.  That means they were burning up lean mass, despite a high (20% of calories) protein, kcalorically adequate diet.  This happened because carbohydrate is protein-sparing.  In other words, eating adequate carbohydrate prevents the use of body protein to produce glucose or glycogen; eating too little carbohydrate leads to the body breaking down lean mass to generate carbohydrate.   This is why many people find it difficult to maintain and especially to build lean mass on a low carbohydrate diet.

What about carbohydrate?  All diets showed positive carbohydrate balance.  This means they were storing carbohydrate, in the form of glycogen, at time of measurement.  Humans are continuosly oxidizing carbohydrate, but intermittently feeding on carbohydrate.  Given adequate dietary carbohydrate, our body's will maintain a positive carbohydrate balance during the day, because we don’t eat at night. This carbohydrate gets burned at night during sleep, when not eating.   Hill et al comment:

As noted above, the body does not regulate energy balance, it regulates balance of nutrients.   The body has different ways of handling each nutrient, in general it avoids converting glucose into fat since it needs glucose and can store it as glycogen.

In the case of carbohydrate, we know that when carbohydrate intake increases, the body increases carbohydrate usage and converts some (about 10%) to heat (thermogenesis), and it stores any excess carbohydrate as glycogen.  It appears that the body regulates carbohydrate stores (glycogen) by increasing carbohydrate oxidation when carbohydrate is abundant and reduces glucose oxidation when dietary carbohydrate is scarce (to conserve glycogen).  Experiments involving overfeeding 500 grams of carbohydrate daily have shown that the body converts very little of this to fat, and only after prolonged overfeeding; after seven days of such overfeeding people produce only about 5-10 g of fat via conversion of glucose.[6 , 7]  Furthermore, conversion of glucose to fatty acids consumes about 25% of the energy in the glucose.  

In the case of dietary fat, when you eat more grams of fat than you burn, you will store those grams of fat in fat stores; the body has no other way to store them, and most research shows most fats do not have a thermogenic action.  The high prevalence of obesity shows that the body does not regulate fat storage effectively.  Since it avidly stores fat without regulation, this suggests that evolutionary diets did not have much fat (avid storage would evolve as a response to scarcity).

So, if you consume 10 g excess fat daily, you will directly store those grams of fat in fat stores.  Over a month, those 10 g of fat add up to 300 g, or about  three quarters of a pound.  The body does not calculate the kcaloric value of those grams of fat; the kcaloric value is simply irrelevant to the body.  I repeat, energy balance is irrelevant.  The body has no means of regulating "energy," a theoretical entity; it only shuffles grams of substances like fat, carbohydrate, and protein.

When you eat fewer grams of fat than you burn, you will release fat from fat stores.  Eat 10 g less fat daily than you burn, and you will lose 300 g of fat per month; to lose one pound of fat weekly, you need to create a fat deficit of about 65 g daily (i.e. consume 65 g less fat than you burn).   

You might be able to achieve this on a low carbohydrate diet, and you might not.  If eating a low carb diet allows you to eat less fat than you burn daily, you will lose fat, and if it doesn’t you will not.  On the other hand, regardless of theoretical "energy" intake, if eating a low carbohydrate diet results in your consuming more fat than your body burns daily, you will increase your body fat day by day. 

In my experience, many people increase fat intake well beyond fat oxidation when eating low carbohydrate diets, in spite of reduced kcalorie intake.

The body does not store "energy," it stores fat or carbohydrate, gram by gram.  A gram of fat is a gram of fat; if you don’t burn it, you will store it.   

All Diets Are Reduced Carbohydrate Diets

I just finished reading Gary Taubes' second blog post entitled "Calories, fat or carbohydrates? Why diets work (when they do)."   Distilled, he pointed out that when you reduce calories, you automatically reduce carbohydrate, which then begs the question, does a reduced calorie diet work primarily because of reduced energy intake, or because of reduced carbohydrate intake?


Gary gives some illustrations of this principle, and I want to expand upon them.  If you've been eating 2500 calories daily with the typical 35% as fat, 15% as protein, and 50% as carbohydrate, you've been getting 875 calories from 97g of fat, 375 calories from 94g of protein, and 1250 calories from 313g of carbohydrate.  


If in seeking weight loss you reduce calories by 500 and fat to the widely recommended 30% of calories, while keeping protein at 15% of calories, your "diet" will now consist of 2000 total calories, with 600 calories from 67g of fat, 300 calories from 75g of protein, and 1100 calories from 275g of carbohydrate.  


This "diet" has reduced fat by 275 calories, protein by 75 calories, and carbohydrate by 150 calories.  Thus, this diet is a reduced calorie and reduced fat diet, but it is also a reduced protein, reduced carbohydrate diet.

 Now, if you do lose body fat, how do you know what caused it?  Was it the reduction of total calories, the reduction of fat calories, the reduction of protein intake, or the reduction of carbohydrate intake?  

Many people will assume that it is the reduced caloric intake that produced the change, or that the reduction of fat intake is "most" responsible since the calorie intake from fat was the most reduced.


In fact, from this experiment, there is no way that you can tell which of these reductions is actually responsible for the reduction of your fat mass, because all of these things have changed.

Researchers continue to act as if reduced calorie diets are NOT reduced carbohydrate diets, when in fact all reduced calorie diets are also reduced carbohydrate diets.  

Taubes also discusses a study published by Shai et al in the New England Journal of Medicine: "Weight Loss with a Low-Carbohydrate, Mediterranean, or Low-Fat Diet [full text]."  He posted this table from the article:

As Gary says, we have to take this data with a shaker of salt since it is from diet records that are notoriously misleading.  Let's set aside the fact that the data collected probably gives us a poor picture of the actual dietary practices of the groups.  If you study it, you find that the so-called "low carbohydrate diet" group reduced their intake of carbohydrate from 50% of energy to 40% of energy over 24 months.   Meanwhile subjects in both the "low fat diet" and the "Mediterranean diet" groups got 50% of energy from carbohydrate.  

This means that the "low carbohydrate" dieters consumed 80% of the amount of carbohydrate as the "low fat" and "Mediterranean" dieters.  Assuming an intake of 2000 calories, the "low carb" group took an average of 800 calories/200g of carbohydrate daily, while the "low fat" and Mediterranean" groups took an average of 1000 calories/250g of carbohydrate daily.  


I don't know anyone in the "low carbohydrate" diet camp who would consider 200g of carbohydrate daily a low carbohydrate diet.  I don't consider a diet low in carbohydrate unless it contains no more than 25% of calories from carbohydrate.  Of interest here, the authors apparently consider 30% of energy from fat to be "low fat," while 40% of energy is "low carbohydrate." 

So, if you are interested in producing a study that shows little or no difference between low carbohydrate diets and low calorie diets for fat loss, all you have to do is to allow the "low carbohydrate" group to eat a diet high in carbohydrates, then call what they did "low carbohydrate" when you write up the results.

Despite this quite obvious lack of rigor, which by the way got past all the peer review process (illustrating what that is worth), the study actually did show that the people eating the "low carbohydrate" diet had the greatest fat loss over 24 months.  According to the authors, "of the 272 participants who completed the intervention, the mean weight losses were 3.3 kg, 4.6 kg, and 5.5 kg" respectively for the "low fat," "Mediterranean," and "low carbohydrate" diets.

Think this through.  An average reduction of only 50g of carbohydrate daily (about 3 slices of bread, two 4-oz potatoes, or 2 pieces of fruit) gave the "low carbohydrate" group a weight loss 67% greater than the low fat group, and 20% greater than the "Mediterranean" group. 

Meanwhile, the "low carbohydrate" group ate more fat than the other groups.  The "low carbohydrate" is reported to have gotten 39% of energy from fat, the Mediterranean 33%, and the "low fat" 30%.  That would translate to 780 calories from 87g fat for a 2000 calorie intake for the "low carbohydrate" group, 660 calories from 73g fat for the "Mediterranean" group, and 600 calories from 67g fat for the "low fat" group.  This data clearly suggests that the more fat you eat, the more fat you will lose; completely opposite to the "low fat" mantra.  While eating 20g more fat per day, the "low carbohydrate" diet group lost an average of 67% more body fat than the "low fat" group. 

In reality, this study compared three different high carbohydrate diets, each with a low fat intake, and found that those who ate the most fat and least carbohydrate had the greatest reduction of body fat.  Yet the popular press presented this as if it doesn't matter whether you reduce fat or carbohydrate, so long as you reduce caloric intake.

Bad science.  As usual.