A calorie-based weight loss system doesn't work for two principle reasons. First, the different macronutrients produce different hormone responses that directly influence the metabolic rate and whether the body is in a fat burning or storing mode.
Second, the amount of calories—known as the thermic effect of food— required for the body to break down different foods varies greatly. For a simple example, your body burns significantly more calories digesting a meal of animal protein and fibrous leafy greens than a meal of carbs such as pasta with tomato sauce. Even fewer calories are required to digest processed foods like cookies, white bread, or potato chips.
Macronutrients Dictate Hormone Responses
The first part of the faulty calorie system of fat loss is that the macronutrient ratios of your diet dictate hormone response. Carbohydrates, particularly those with a higher glycemic index, immediately increase the level of the hormone insulin.
When you eat a lot of carbs—as is common in calorie-counting diets in which a person eats low-fat, high carb-foods—you will be consistently driving up insulin. Chronically elevated insulin makes the cells resistant to the insulin, which drives up levels of the stress hormone cortisol, causing cellular aging. The combination produce fat gain and diabetes.
If you were substituting protein and “smart” fats for a portion of those carbs, the protein would be used to restore tissue and build lean mass, while the fats would be used to strengthen cellular lipid layers to improve insulin sensitivity, restore brain health, and build hormones like testosterone.
Calorie Restriction Alters Hormonal Response
Restricting calories to lose fat over the long term is more detrimental to your metabolism because it will turn your body into a hormone-induced hunger machine. A study in the New England Journal of Medicine found that after putting overweight individuals on a ten-week calorie-restricted diet of 550 calories a day, they experienced elevated levels of the hormones ghrelin, which stimulates hunger, and gastric inhibitory polypeptide, which promotes fat storage. Leptin, a hormone that suppresses hunger and boosts fat burning, was profoundly reduced after the ten-week diet and stayed that way for the duration of the one-year study.
After the ten-week diet, participants lost 30 pounds, but due to the way they had severely altered their metabolic hormone responses to food by restricting calories, they regained an average of 15 pounds in the next year.
The Thermic Effect of Food
A number of mainstream media outlets incorrectly took the results of a new study published in the Journal of the American Medical Association and proclaimed, “It’s the calories, stupid” that dictate body composition and weight gain.
A close look at the study clarifies the misinterpretation and tells us exactly the opposite: it’s primarily the macronutrient content of the food you eat that dictates body composition, but if you overeat every day, then you will get fat.
The study compared the effect of overeating on body composition and fat gain from diets with three different protein contents. The thermic effect of the different diets was also measured, which is the amount of calories required to break down food, synthesize enzymes, and perform metabolic processes.
Participants ate either 5, 15, or 25 percent of their diet from protein with a whopping extra 954 calories a day for eight weeks. All the diets consisted of well over 3,000 calories a day and the macronutrient content was as follows:
- a “low” protein diet contained 5 percent protein, 52 percent fat, and 42 percent carbs
- a “normal” protein diet had 15 percent protein, 44 percent fat, and 42 percent carbs
- a “high” protein diet had 25 percent protein, 33 percent fat, and 41 percent carbs
All three groups gained the same amount of fat from the overeating—about 3.5 kg. What was most interesting was that the low-protein diet group gained the least total body weight because along with the 3.5 kg of fat gain, they lost almost a kilogram of muscle mass. The lack of amino acid building blocks in the diet put them into a severely catabolic, fat-storing state.
In comparison, the normal-protein diet group gained 2.9 kg of muscle mass and the high-protein diet group gained 3.4 kg of muscle. Therefore, along with the nearly 3.5 kg of fat they gained, the normal- and high-protein diets did produce more weight gain.
But, from a body composition viewpoint, the normal- and high-protein diets were better even though participants gained more total weight than the low-protein group because their percentage of body fat went down.
Most significant, this study shows the extreme variation in the amount of calories burned on a daily basis from eating different proportions of macronutrients. The resting metabolic rate (RMR) is the amount of calories burned at rest during the day, and it’s highly influenced by dietary makeup and the thermic effect of food. The group that ate the low-protein diet experienced a 2 percent drop in their metabolic rate, meaning they burned less calories each day just from eating a low-protein diet.
In contrast, the normal- and high-protein diets increased RMR by 11 percent in response to the higher protein intake. This meant that by eating more protein, more of the energy consumed was turned into lean mass, and only about 50 percent of the energy consumed was turned into fat. Researchers estimate that more than 90 percent of the energy consumed in the low-protein group was turned into fat.
Whole and Processed Calories Aren’t the Same Either
A second study shows that the RMR and the thermic effect of eating whole foods is much higher than if you ate the exact same amount of calories from processed foods. This study compared the effect of a whole foods meal with a processed foods meal that contained equal calories and equal macronutrient content.
The thermic effect of the whole food meal was almost double that of the processed food meal. Participants burned 50 percent more calories after eating whole foods!
Equally significant is that the participants who ate the processed food meal had their metabolic rates drop below their average RMR during the fourth hour after eating, while the whole food meal group never fell below the RMR. Also the duration of elevated energy expenditure from digestion in the whole food meal group lasted an hour longer than the processed food group.
Take Away Points
For optimal body composition, the solution to any remaining confusion about how to adopt a diet for fat loss is to understand the following:
- A protein calorie is NOT the same as a carbohydrate calorie.
- The thermic effect of different macronutrients varies just as the thermic effect of processed foods is much less than of whole foods.
- Macronutrient ratios will determine hormone response.
- The total amount of calories you eat in a day DO matter for body composition—if you are overeating as in the study that had participants eating an extra 954 calories a day, you will gain weight, but whether that weight results in fat or muscle gain depends on macronutrient ratios.
- If you aren’t overeating, simply altering the macronutrient ratios to manage insulin and the hormone response of food can lead to fat loss and significantly improve body composition.