Apparently a low carb diet causes increased weight loss…
What You’ll Takeaway –
1. Many believe low carb diets can result in increased weight loss and some even claim without any calorie deficit, resulting in an advantage over other higher carb diets.
2. BUT what is normally overlooked is the protein content when the 2 diets were compared.
3. Protein has been shown to a higher thermic effect, the amount of energy lost through digestion, compared to carbohydrate and fat.
4. It cannot be denied though a calorie is a calorie (4.2 joules) but it is stupid to believe 100 calories of steak is similar to 100 calories of brownies due to the different macronutrients, micronutrients and fibre content.
In 2012, Ebbeling CB et al. carried out research into the effect of isoclaoric diets, with different macronutrient make ups, on weight loss; a low-fat diet (60% of energy from carbohydrate, 20% from fat, 20% from protein; high glycemic load), low-glycemic index diet (40% from carbohydrate, 40% from fat, and 20% from protein; moderate glycemic load), and very low-carbohydrate diet (10% from carbohydrate, 60% from fat, and 30% from protein; low glycemic load)
They concluded ‘Among overweight and obese young adults compared with pre-weight-loss energy expenditure, isocaloric feeding following 10% to 15% weight loss resulted in decreases in REE and TEE that were greatest with the low-fat diet, intermediate with the low-glycemic index diet, and least with the very low-carbohydrate diet.’ In English this means they found that a person’s metabolism was higher in the group eating the low-carb, burning more calories during the day.
This has led people to claim low carb diets can result in increased weight loss and some even claim without any calorie deficit, resulting in an advantage over other higher carb diets. Other recent studies found that low-carbohydrate diets do yield greater weight loss compared to a high carb even when calories were matched. (1-3) People have been jumping to the conclusion low carbohydrates are best ever since!
BUT what is normally overlooked is the protein content when the 2 diets were compared.
So can protein influence calorie expenditure?
In all of these experiments the low carb diets had a higher protein content compared to the high carb diet. This is important because protein has been shown to affect your total daily expenditure. Total daily energy expenditure is made of 4 components; basal metabolic rate, thermic effect of food (TEF,) non-exercise activity thermogenesis and physical activity.
Protein has been shown to a higher thermic effect, the amount of energy lost through digestion, compared to carbohydrate and fat. (5) Along with stimulating the increase in lean body mass, which contributes to a slight increase in metabolism. So it can obviously increase your total energy expenditure. It is also important to remember that stored carbohydrate, glycogen, additionally carries 3 grams of water for every gram of glycogen. Therefore when on a low carb diet, lower glycogen stores will result in an initial rapid drop in bodyweight due the loss in water, not necessarily fat! This would mean a low carb diet would show a great weight loss over acute experiments,
A reverse experiment was carried out to show the effect protein has on energy expenditure when overfeeding in a metabolic chamber. (6) Diets all consisted of +40% calorie surplus from either from 5%, 15%, or 25% protein for 56 days with constant carb intake. Results shows that a lower protein diet did not acutely increase 24hr energy expenditure, but it slowly raised as body weight increased. Excess energy from a high protein intake acutely (short term) stimulated 24hr energy expenditure to a far higher degree. This is more proof that protein can affect your energy expenditure.
This has led many people to believe and claim that a calorie is not a calorie because of the effect different macronutrients have.
It cannot be denied though a calorie is a calorie (4.2 joules) but it is stupid to believe 100 calories of steak is similar to 100 calories of brownies due to the different macronutrients.
Research carried out into the question is a calorie a calorie concluded –
‘We conclude that a calorie is a calorie. From a purely thermodynamic point of view, this is clear because the human body or, indeed, any living organism cannot create or destroy energy but can only convert energy from one form to another. In comparing energy balance between dietary treatments, however, it must be remembered that the units of dietary energy are metabolizable energy and not gross energy.’ (4)
(This is summed up in the diagram below showing the loss in energy through digestion. The gross energy is what the food contains and metabolizable energy is what the body is able to use. This is due to waste production and the amount of energy released during digestion.)
‘In addition, we concede that the substitution of one macronutrient for another has been shown in some studies to have a statistically significant effect on the expenditure half of the energy balance equation. This has been observed most often for high-protein diets. Evidence indicates, however, that the difference in energy expenditure is small and can potentially account for less than one-third of the differences in weight loss that have been reported between high-protein or low-carbohydrate diets and high-carbohydrate or low-fat diets. As such, a calorie is a calorie. Further research is needed to identify the mechanisms that result in greater weight loss with one diet than with another.’ (4)
Does this mean eating more protein results in great weight loss?
No, not if you were eating into a calorie surplus or at maintenance. In order to lose weight you need to create a calorie deficit, just because food has different effects on thermogenesis this does not mean that calories do not matter. Consuming adequate ratios of pro, carbs and fats will aid in the process of increased weight loss, improved performance and muscle growth, satiety and improved health.
So saying that ‘a calorie is a calorie’ can cause confusion and arguments if people do not take macronutrients into account. People assume all macronutrients have the same thermogenic effect during digestion within the body which we know is not true. So in my opinion stop using the term ‘a calorie is a calorie’ as it is just starting unnecessary confusion, and look more to macronutrients which make up calories.
So remember a calorie is a calorie and the distinction different between gross energy and net energy!
1. Gary D. Foster, Ph.D., Holly R. Wyatt, M.D., James O. Hill, Ph.D., Brian G. McGuckin, Ed.M., Carrie Brill, B.S., B. Selma Mohammed, M.D., Ph.D., Philippe O. Szapary, M.D., Daniel J. Rader, M.D., Joel S. Edman, D.Sc., and Samuel Klein, M.D. A Randomized Trial of a Low-Carbohydrate Diet for Obesity. N Engl J Med 2003; 348:2082-2090May 22, 2003
2. A R Skov1, S Toubro1, B Rønn2, L Holm1 and A Astrup. Randomized trial on protein vs carbohydrate in ad libitumfat reduced diet for the treatment of obesity. May 1999, Volume 23, Number 5, Pages 528-536
3. Bonnie J. Brehm, Randy J. Seeley, Stephen R. Daniels, and David A. D’Alessio. A Randomized Trial Comparing a Very Low Carbohydrate Diet and a Calorie-Restricted Low Fat Diet on Body Weight and Cardiovascular Risk Factors in Healthy Women. The Journal of Clinical Endocrinology & Metabolism, Volume 88, Issue 4
4. Andrea C Buchholz and Dale A Schoeller. Is a calorie a calorie? Am J Clin Nutr May 2004vol. 79 no. 5 899S-906S
5. Jéquier E1. Pathways to obesity. Int J Obes Relat Metab Disord. 2002 Sep;26 Suppl 2:S12-7.
6. George A Bray, Leanne Redman, Lilian de Jonge, Jeffrey Covington,Jennifer Rood, Courtney Brock, Susan Mancuso, Corby K Martin, and Steven R Smith. Effect of protein overfeeding on energy expenditure measured in a metabolic chamber. Am J Clin Nutr March 2015 ajcn.091769.