Calories DO matter. But it is crucial to understand in what way. A conventional explanation of a calorie and its role in weight loss is extremely simplified and not always applicable to an actual human body functioning.
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The first law of thermodynamics says that body mass remains constant when caloric intake equals caloric expenditure. It is noteworthy that different diets lead to different biochemical pathways. They are not equivalent when compared to the laws of thermodynamics. It is wrong to assume that the only thing that matters regarding eating and energy balance is the absorption of dietary calories and weight storage. Well-made studies suggest that calories content may not be as predictive of fat loss. Biologically, a calorie is certainly not a calorie.
The hormonal changes associated with a low-carbohydrate diet include a reduction in the circulating levels of insulin along with increased levels of glucagons. It is leading to activation of certain enzymes, favoring gluconeogenesis over glycolysis. Gluconeogenesis is an energy-consuming process. The conversion of gluconeogenic amino acids into glucose requires even more energy. Furthermore, a low-carbohydrate diet increases turnover of body proteins; and the energy-dependent processes of maintaining the turnover of proteins has an overall cost to body energy homeostasis that is significantly higher than previously appreciated.
Also, a low-carbohydrate diet is usually high in protein. A study demonstrated that thermogenesis increases on a high-protein/low-fat diet vs. a high-carbohydrate/low-fat diet in healthy subjects. Finally, ketogenic diets are designated by elevations of free fatty acids, leading to the increased transcription of mitochondrial uncoupling proteins, resulting in the generation of heat rather than ATP. Also, fatty acids undergoing this process have no mechanism for energy conservation and result solely in heat production.
The important thing to note is that this leads to metabolic inefficiency.
“A paper intended as a systematic review concluded, “weight loss while using low-carbohydrate diets was principally associated with decreased calories intake and increased diet duration, not with reduced carbohydrate content.” However, in the real low-carbohydrate group in the research, the typical weight loss in trials was 17 kg, whereas in the high-carbohydrate group it was just 2 kg. Authors did not consider this vital. As Kauffman stated, “the conclusions should have been that low-carbohydrate diets are both safe and efficient.”
Only by mixing trials of low to medium and high-carbohydrate diets could the authors reach the misleading conclusion quoted above.
A recent report concluded that a low-carbohydrate diet produced a greater weight loss than the traditional nutrition for the first six months, but the differences were not significant at one year. Samaha et al. randomly assigned 132 severely obese subjects to a low-carbohydrate or calories and fat-restricted (low-fat) diet. Seventy-nine subjects completed this six-month study.
It is noteworthy that the variation in energy gathered from carbohydrate was quite small. The low-carbohydrate group consumed 54 extra kcal/day. Nonetheless, the low-carbohydrate group lost 5.8 kg (and was still losing weight at six months mark) while the low-fat group lost 1.9 kg (leveled off). Both groups had a considerable amount of meetings with “specialists in nutritional consulting,” so the possible placebo and nocebo effects would be high here.
Researchers found that people who eat an extra 300 kcal a day on a very-low-carbohydrate diet lose a similar amount of weight during a 12-week study as those on a low-fat diet. In the study, subjects consumed an extra 25,000 kcal that should have added up to about a 7 pounds weight gain – it did not. The study was unique because people prepared all the food at an upscale establishment, so the researchers exactly knew what they ate.
Finally, a recent randomized, balanced, two diet research compared effects of isocaloric, energy-restricted ketogenic and low-fat diets on weight loss and body composition. They tested this on overweight/obese men and women. Despite significantly greater calories intake, both between and within group observation revealed a distinct advantage of a low-carbohydrate diet over a low-fat diet for weight loss/fat loss for men. In fact, five men presented more than 10 pounds variety in weight loss. The majority of women also responded much better to the ketogenic diet, especially regarding trunk fat loss.”
Although the weight loss has obvious significance, an equally important question is related to the composition of weight loss. There is a study of the effect of a ketogenic diet on the composition of weight loss. Researchers observed that when a 1,000-kcal ketogenic diet was fed for ten days, their subjects lost an average of 600 g/day – 97% of this was fat. Researchers compared three isoenergetic (1,800 kcal/day) and isoprotein (115 g/day) diets differing in carbohydrate content. After nine weeks on the 30g, 60g, and 104g content of sugar in the diet, weight change was -16.2, -12.8, and -11.9 kg; 95%, 84%, and 75% of the weight loss was fat, respectively.
Recently, researchers examined the effects of 6-week very-low-carbohydrate diet on total and regional body composition. Interestingly, their results indicated that fat mass was significantly decreased and lean body mass increased. A low-carbohydrate diet led to significant reduction in serum insulin concentrations. There was a significant correlation between the reduction in insulin and the decrease in body fat.
Finally, scientists examined the efficacy and metabolic impact of a ketogenic diet in the treatment of obese adolescents. The authors stated that ketogenic diet is “a safe and effective weight loss regimen. The weight loss with this approach is rapid, consistent, and almost exclusively from body fat stores”. People claim that weight loss with those diets is explained by dehydration. However, the study demonstrated that alterations in the water and electrolyte balance during the low-carbohydrate diets are reversible and should thus not be regarded as causal agents of the different weight reduction. Also, the current studies did not find any indication of an excessive reduction in lean body mass. Therefore, the greater weight loss is attributable to fat loss.”
“There is evidence that hyperinsulinemia increases fat mass without a concomitant growth in energy intake. Six patients with diabetes were studied on an insulin therapy. After two months of it, while maintaining a constant calories intake, they compared them with six non-diabetic volunteers. The results showed that two months of intensive insulin therapy improved glycemic control dramatically. However, this improvement caused weight gain. The result was an increase in fat mass and not lean body tissue.
There is evidence indicating that low-glycemic diets influence body weight and resting energy expenditure independently of caloric intake.
It is frequently more clear that the idea that “a calorie is a calorie” is misleading. The calorie content may not be a good indicator of possible change in body composition. Different diets lead to different biochemical pathways (due to the hormonal and enzymatic changes). They are not equivalent when correctly compared through the laws of thermodynamics. Unless one measures heat and the biomolecules synthesized using ATP, it is improper to assume that the only thing that counts regarding food consumption and energy balance is the intake of dietary calories and weight storage.
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