Journal Logo

OBESITY AND NUTRITION: Edited by Eric C. Westman

A case study of overfeeding 3 different diets

Feltham, Sama; Westman, Eric C.b

Author Information
Current Opinion in Endocrinology & Diabetes and Obesity: October 2021 - Volume 28 - Issue 5 - p 446-452
doi: 10.1097/MED.0000000000000668
  • Open

Abstract

INTRODUCTION

For decades, experts have taught that obesity is caused by excessive caloric intake relative to expenditure and that the macronutrient composition of the calories was of lesser importance, or of no importance at all. Obesity is the ‘result of disequilibrium between energy intake and expenditure [1].’ The problem with focusing on calorie/energy balance as the explanation for obesity is that it does not ask why there is an imbalance, and whether different macronutrients may have different hormonal effects [2].

If the macronutrient composition of the diet is irrelevant, then caloric restriction to the same level would have absolutely the same effect. However, several observations suggest otherwise. Recent randomized, controlled trials comparing low-carb to low-fat diets show different effects in terms of weight loss, and changes in cardiometabolic risk factors [3]. More carefully controlled studies of metabolic rates can detect differences in changes for different diets of the same caloric level, but different macronutrient composition [4,5▪▪].

If the macronutrient composition of the diet is irrelevant, then overfeeding of the same level of calories should lead to the same amount of weight gain. Several recent reviews of overfeeding studies show a remarkable lack of studies comparing diets that span the entire macronutrient range [6▪]. For example, there were no studies comparing overfeeding with a very high carbohydrate diet to a very low carbohydrate diet.

With a literature review leading to no answer to the question of overfeeding of different diets, one of the authors (S.F.) designed and performed an n-of-1, three-period, cross-over study using himself as the study subject. The research question was ‘does overconsuming 3 diets of different macronutrient composition lead to the same effects on body composition?’ The amount of 5800 daily Calories was chosen to ensure weight gain over the 21-day time period. The diets were chosen based upon the macronutrient composition of diets that are currently popular: low-carb/keto, low-fat and very-low-fat vegan. 

Box 1
Box 1:
no caption available

METHODS

The subject was a Caucasian male age 29 years old. Each diet was followed over a 21-day period, and the target caloric intake was 5,800 kilocalories per day. The diet periods were separated by a 3-month ‘wash-out’, or ‘return to baseline’ period. The order of the diet periods was low-carb, low-fat, very-low-fat vegan.

Low-carb diet

The low-carb diet itself consisted of fish, eggs, steak, green beans and nuts. Table 1 shows the description of foods and calculation of the caloric and macronutrient intake.

Table 1 - Description of the low-carb diet: daily food intake
Food and drink Calories (kcals) Carbohydrates (g) Protein (g) Fat (g)
Breakfast
 Coconut oil (15g) 135 0 0 15
 Salmon (200g) 374 0.4 48.2 19.8
 Green Beans (180g) 60 18 2 0
 Eggs (250g) 390 3 31.5 26.5
Snack 1
 Walnuts (150g) 1058 4.6 25.95 102.75
Lunch
 Coconut oil (15g) 135 0 0 15
 Green Beans (180g) 60 18 2 0
 Mackerel (260g) 785 5.2 48.1 62.92
Snack 2
 Pecans (150g) 1059 8.25 16.35 105.15
Dinner
 Coconut oil (15g) 135 0 0 15
 Green Beans (180g) 60 18 2 0
 Topside Beef (400g) 576 0 108 15.6
Snack 3
 Almonds (150g) 967 9.75 38.1 83.7
 Grand Totals: 5794 85.2 322.2 461.42
Pct of Calories: 5.9% 22.3% 71.8%

The macronutrient breakdown was 6% carbohydrates, 72% fat and 22% protein.

Low-fat diet

The diet itself consisted of breakfast cereal, skimmed milk, mini-pizza, 0% fat yoghurt, wholemeal bread, chicken, reduced fat rice pudding, coke, lasagne, garlic bread, and chocolate. Table 2 shows the description of foods and calculation of the caloric and macronutrient intake. The macronutrient breakdown was 64% carbohydrates, 23% fat, and 13% protein.

Table 2 - Description of the low-fat diet: daily food intake
Food and drink Calories (kcal) Carbohydrates (g) Protein (g) Fat (g)
Breakfast
 Kellogg's bran flakes (100g) 344 67 8 2
 Skimmed milk (300ml) 111 14.7 10.8 0.3
 2 Crumpets 240 47.8 7.8 1.2
 Strawberry jam (100g) 244 60.6 0.4 0
Snack 1
 Mini cheese and tomato pizza (500g) 1085 216.5 34 9.5
 0% Fat strawberry yoghurt (330g) 202 33 16.6 0.4
 Can of coke (330ml) 139 35 0 0
Lunch
 2 Slices of Wholemeal Bread 210 33.2 9.2 3.4
 Chicken tikka filler (100g) 135 7.1 13 5.9
 1 Chocolate Muffin (105g approx.) 440 64.9 7.5 16.1
Snack 2
 Cheese and onion crisps (35g) 181 18.8 2.8 10.5
 Reduced fat rice pudding (500g) 395 46.5 14 3
 Can of coke (330ml) 139 35 0 0
Dinner
 Cheese and pepperoni lasagne (400g) 536 54 28.8 21.6
 Garlic bread (100g) 365 43.1 7.6 17.3
Snack 3
 Chocolate bubbly bites (150g) 825 82.5 11.55 49.2
 0% Fat strawberry yoghurt (330g) 202 33 16.6 0.4
 Grand Totals: 5793 892.7 188.65 140.8
Pct of calories 63.9% 13.5% 22.6%

Very-low-fat vegan diet

The diet itself consisted of porridge, soya milk, banana, various beans, olive oil, potato, rice, tofu, avocado, apples, mandarins, and pineapple. Table 3 shows the description of foods and calculation of the caloric and macronutrient intake. The macronutrient breakdown was 68% carbohydrates, 15.5% fat, and 16.5% protein.

Table 3 - Description of the very-low-fat vegan diet: daily food intake
Food and drink Calories (kcal) Carbohydrates (g) Protein (g) Fat (g)
Breakfast
 Porridge (250g) 890 150 27.5 20
 Banana (250g) 257.5 58 3 0.75
 Soya milk (250ml) 61 3.5 5 3
 Dried apricots (125g) 222.5 45 4.88 0.75
Snack 1
 Pinto beans (525g) 525 78.75 36.75 0
 Chopped tomatoes (390g) 94 17.2 3.6 0.8
 Olive oil (10ml) 82 0 0 9.14
Lunch
 Jacket potato (500g) 750 158.5 19.5 1
 Chestnuts (200g) 326 63.2 8.6 2
 Olive oil (10ml) 82 0 0 9.14
Snack 2
 Borlotti beans (350g) 385 64.4 28 1.76
 Blackeye Beans (350g) 444.5 63.36 30.8 2.46
 Butter beans (235g) 228 30.55 14.57 1.65
 Olive oil (10ml) 82 0 0 9.14
Dinner
 Rice (500g as consumed) 595 130 13 1
 Tofu (349g) 216.38 6.98 24.43 10.47
 Avocado (120g) 229.2 2.28 2.28 24.4
 Peas (100g) 81 9.7 6 0.9
Snack 3
 Apples (200g) 102 24 0.8 0.2
 Mandarins (200g) 36 12 1.6 0.2
 Pineapple (200g) 88 20.2 0.8 0.4
 Agave nectar (6g) 17 4.5 0 0
 Daily totals: 5794.08 942.12 231.11 99.16
Pct of calories: 68.0% 16.5% 15.5%

Exercise/activity

The subject kept his activity/exercise the same during all diet periods. His weekly exercise totaled 3 h of cycling (commuting to work) and a 20 min high-intensity interval training workout three times per week.

Outcomes

Caloric intake. The daily Caloric intake was estimated using food labels on packets and nutritional information available a supermarket website: www.asda.com.

Total body weight. The body weight was measured on the same scale and was the average of the first morning and evening weight in short pants.

Waist circumference. The waist circumference was measured at the level of the umbilicus and was the average of the first morning and evening waist measurements.

Body shape. A photograph of the subject from the side was taken at the beginning, middle, and end of the diet periods.

Subjective report. General observations were reported for each diet period.

RESULTS

Low-carb diet

During this period, the estimated Caloric intake was 121,674 kilocalories. The body weight increased 1.3 kg, from 85.6 to 86.9 kg. The waist circumference decreased 3 centimeters.

The changes in body shape for the low-carb diet period are shown in Fig. 1.

FIGURE 1
FIGURE 1:
Side profile photos of day 1, day 10 and day 21 of the low-carb diet.

Subjective report. ‘My experience during this diet was mainly a happy one. I had lots of energy, could exercise normally and I was never hungry. In fact at certain points during the low-carb diet I had to force feed myself when I was full. Especially in the evening when I had to eat 967 k/cals of almonds after 771 k/cals of steak and green beans.’

Low-fat diet

During this period, the estimated Caloric intake was 121,653 kilocalories. The body weight increased 7.1 kg, from 89.7 to 96.8 kg. The waist circumference increased 9.25 centimeters. The changes in body shape for the low-fat diet period are shown in Fig. 2.

FIGURE 2
FIGURE 2:
Side profile photos of day 1, day 10 and day 21 of the low-fat diet.

Subjective report. ‘My experience during this diet was not a happy one. Within 3 days my asthma had returned, which made it difficult to breathe during exercise and whilst I was sleeping. This in turn disrupted my sleep and I began to snore. In general, I felt lethargic and cognitively foggy. Converse to the low-carb diet, on the low-fat diet I easily ate all the food by the end of the day and probably could have managed more.’

Very-low-fat vegan diet

During this period, estimated Caloric intake was 121,674 kilocalories. The body weight increased 4.7 kg, from 87.3 to 92.0 kg. The waist circumference increased 7.75 cm. The changes in body shape for the very-low-fat vegan diet period are shown in Fig. 3.

FIGURE 3
FIGURE 3:
Side profile photos of day 1, day 10 and day 21 of the very-low-fat vegan diet.

Subjective report. ‘My experience during this diet was not a happy one. My fiber intake was 178 g per day, and so the main side effect was that I was having to go to the toilet a lot, which was unsettling. Cognitively I was also foggy and after about 10 days my asthma had returned, which made it difficult to breathe during exercise and whilst I was sleeping. The difference with the low-fat diet was that I was not hungry. Similar to the low-carb diet, at certain points during the day I had to force feed myself.’

A comparison of the results from each diet period shows a large difference weight gain and change in abdominal circumference (Table 4). There was a 5-fold difference in weight gain, and the low carbohydrate diet led to a reduction in waist circumference, whereas the low-fat and very-low-fat vegan diets led to increases in waist circumference.

Table 4 - Effects of overfeeding 3 different diets for 21 days on body composition
Diet Calories/day Carbohydrate Protein Fat Change in weight kg Change in waist circumference cm
Low-carb 5794 5.9% 22.3% 71.8% +1.3 −3.0
Ultra-low-fat vegan 5794 68.0% 16.5% 15.5% +4.7 +7.75
Low-fat 5793 63.9% 13.5% 22.6% +7.1 +9.25

CONCLUSION

Based on the notion that a ‘calorie is a calorie,’ very little difference should be observed when overfeeding 3 diets of the same caloric value but different macronutrient compositions. In this preliminary investigation, large differences were found in body composition when overconsuming 3 diets with different macronutrients, and suggest that ‘a calorie is NOT a calorie’ inside the human body—at least in the context of overfeeding [7,2].

Because of the clinical observation that ‘individuals following a low carb diet seem to be able to eat more and lose more weight,’ and the metabolic differences of different diets, we suspected there would be differences between the 3 diets, but we were surprised to see the differences of this magnitude. The difference in weight gain was from 1.3 to 7.1 kg over just 21 days. These results are consistent with the weight loss studies. In many outpatient randomized trials, low carbohydrate diets lead to greater weight loss than low-fat diets [8]. Several outpatient studies have examined a wider range of macronutrient patterns for weight loss [9,10]. To our knowledge, there has never been a similar 3-arm clinical trial looking at the mechanisms of weight gain for these specific dietary patterns.

It is possible that the biochemistry involved in processing different foods reason leads to such differing outcomes between the diets. One possible explanation may be the differences in the glycemic index/insulin response of foods: the low-carb diet was made up of low insulin response foods, the low-fat diet was made up of high insulin response foods and the very-low-fat vegan diet was made up of medium/high insulin response foods [2].

The limitations of this study include just one subject was studied, and he was generally in good health and exercised regularly, so these findings may not apply to a individuals with medical problems. Additionally, these results may not extrapolate to ALL types of low-carb or low-fat diets, as there is a wide range of food choices within each of these general diet descriptions.

This observation of such a surprising finding in just one individual calls for replication in larger, well-controlled studies. If these findings are replicated, there are many implications for obesity treatment and dietary guidelines in terms of macronutrient recommendations. Furthermore, it would suggest that measuring calories as units of energy in physics is not translatable to how they are processed inside the human body.

Acknowledgements

The authors are grateful to everyone who has taken an interest in S.F.'s self-experiments over the years. However, a special mention must go to Prof Richard D. Feinman, who has been particularly supportive.

Financial support and sponsorship

No financial support or sponsorship has been given.

Conflicts of interest

S.F. has no conflicts of interest. E.C.W. receives royalties for the sale of diet books, and has equity in Adapt Your Life, Inc., a company based on low-carbohydrate concepts.

REFERENCES AND RECOMMENDED READING

Papers of particular interest, published within the annual period of review, have been highlighted as:

▪ of special interest

▪▪ of outstanding interest

REFERENCES

1. González-Muniesa P, Mártinez-González MA, Hu FB, et al. Obesity. Nat Rev Dis Primers 2017; 3:17034.
2. Ludwig DS, Ebbeling CB. The carbohydrate-insulin model of obesity: beyond ‘calories in, calories out.’. JAMA Intern Med 2018; 178:1098–1103.
3. Bueno NB, de Melo ISV, de Oliveira SL, da Rocha Ataide T. Very-low-carbohydrate ketogenic diet v. low-fat diet for long-term weight loss: a meta-analysis of randomised controlled trials. Br J Nutr 2013; 110:1178–1187.
4. Hall KD, Bemis T, Brychta R, et al. Calorie for calorie, dietary fat restriction results in more body fat loss than carbohydrate restriction in people with obesity. Cell Metab 2015; 22:427–436.
5▪▪. Ludwig DS, Dickinson SL, Henschel B, et al. Do lower-carbohydrate diets increase total energy expenditure? An updated and reanalyzed meta-analysis of 29 controlled-feeding studies. J Nutr 2021; 151:482–490.
6▪. Bray GA, Bouchard C. The biology of human overfeeding: a systematic review. Obes Rev 2020; 21:e13040.
7. Feinman RD, Fine EJ. ‘A calorie is a calorie’ violates the second law of thermodynamics. Nutr J 2004; 3:9.
8. Nordmann AJ, Nordmann A, Briel M, et al. Effects of low-carbohydrate vs low-fat diets on weight loss and cardiovascular risk factors: a meta-analysis of randomized controlled trials. Arch Intern Med 2006; 166:285–293.
9. Gardner CD, Kiazand A, Alhassan S, et al. Comparison of the Atkins, Zone, Ornish, and LEARN diets for change in weight and related risk factors among overweight premenopausal women: the A TO Z Weight Loss Study: a randomized trial. JAMA 2007; 297:969–977.
10. Shai I, Schwarzfuchs D, Henkin Y, et al. Weight loss with a low-carbohydrate, Mediterranean, or low-fat diet. N Engl J Med 2008; 359:229–241.
Keywords:

low-carb; low-fat; overfeeding; vegan; weight gain

Copyright © 2021 The Author(s). Published by Wolters Kluwer Health, Inc.