What proponents of low-carbohydrate diets seem to miss is the obvious. Even though CHO and protein stimulate insulin release and lead to storage of substrate as FA, it will not lead to long-term fat accumulation unless caloric intake exceeds caloric expenditure for that day, or week, etc. These proponents take a complex series of events (human metabolism), highlight the portion that supports their claim and ignore the big picture. Because humans are periodic eaters, we will always eat more at a sitting than can be immediately used for energy. This influx of glucose, amino acids, glycerol and fatty acids stimulate insulin release so that these materials can be used for energy and stored for later use (as glycogen in liver and muscle and fat stores).5 As an individual goes through the next several hours without food intake, fatty acids and glucose are liberated from storage depots to fuel metabolic activity that is always occurring.
By the way, in a resting state, fatty acids provide the majority of energy used, regardless of diet composition. We are storing and liberating fat continuously throughout the day. There is absolutely no evidence that a high CHO diet will lead to weight gain if one eats at or below maintenance. In fact, it is impossible. In the end it is caloric intake versus expenditure that determines if one increases or decreases fat stores.
Also, if one looks at the energy cost of converting macronutrients to fat, it requires much less energy to convert dietary fat to body fat than to convert CHO to body fat (5 percent of calories vs. 20-25 percent).28 A study designed to measure lipoprotein lipase (LPL, a fiat storage enzyme) activity in adipose tissue and skeletal muscle on a high carbohydrate or high fat diet inadvertently illustrated this. The study design was to keep participants in calorie balance, so that weight was not gained or lost. Due to the increased TEF, the participants on the high carbohydrate diet had to eat approximately 300 calories more to maintain body weight than the high fat diet group.
Lastly, one of the biggest concerns associated with high-fat and protein diets, is the impact on health of the individual. High-protein diets are known to increase bone-mineral losses (calcium in particular) and tend to include greater intakes of saturated fats and cholesterol, which contribute to dyslipidemia.29,30 Populations that eat diets lower in protein and fat, and higher in carbohydrates, have the lowest incidences of cardiovascular disease. It is when a culture adopts a Western diet, high in calories, fat and sugar and increases their reliance on technology that obesity and its health problems emerge.31,32,33
If the preceding information is not convincing enough that high-protein diets are not the answer for long-term fat loss in exercising individuals, consider this: of the 438 initial enrollees of the National Weight Control Registry (having lost an average of 66.0 lbs. for over five years), none were successful by following a low-carbohydrate, high-fat diet. In fact, the common denominator for success dietarily was a low-fat diet with a macronutrient profile of approximately 20 percent protein, 25 percent fat and 55 percent carbohydrate.34
This information, from a study published in the Journal of the American Dietetic Association, is the most comprehensive study of its kind to date. Data from many other studies support this.35,36,37,38,39
Before concluding, consider these real-world examples: Endurance athletes, who typically consume between 60-75 percent of their calories from CHO, are some of the leanest people on the planet. Conversely, Inuit Eskimos, who consume only protein and fat, comprise the fattest culture in the world.
A Final Thought
Much time and energy is spent searching for the causes of obesity. Blame is placed on specific foods, classes of macronutrients and genetics. Adding to the confusion is the erroneous belief that the obese maintain very high bodyweights despite low caloric intakes. Many studies show that as body weight increases, reported caloric intake decreases. A recent study showed that self reported energy intakes in American women are approximately 750-1000 calories below energy expenditures as calculated by the doubly labeled water method.40 This discrepancy increases as body mass index (BMI) increases. This is more proof that obesity is, at its most basic level, an issue of energy imbalance. This imbalance perpetuates itself through a combination of constantly available, palatable food and a society that promotes a sedentary lifestyle.
