Do Calories Matter on a Keto Diet?
- Nov 07, 2018
The ketogenic diet first gained fame through its effectiveness for weight loss. The high-fat, low-carb diet promotes nutritional ketosis–a normal metabolic state marked by moderate levels of ketones in the blood. The idea with carb restriction in terms of weight loss is that it prompts the release of body fat to be burned or converted to ketones for energy (extra dietary fat also contributes to ketone production).
For decades, much of dieting focused on counting caloric intake. But not keto.
Let’s explore why you should be paying more attention to the types of food consumed instead of that little number on the back of a nutrition label.
Are All Calories Created Equal?
The question sparking hot debates in scientific circles!
The first law of thermodynamics (or the law of conservation of energy) states that energy cannot be created or destroyed. When applied to weight control, this law translates to the basic formula:
weight gain = energy (calories) in - energy (calories) out
This traditional viewpoint argues that the food eaten is unimportant–a calorie is a calorie. To lose weight, create a calorie deficit by either eating less or burning more. To gain weight, increase calorie intake.
The opposing viewpoint maintains that calories still count, but the type of food consumed has a trickle-down effect on the amount of energy expended, and what foods the body craves. It takes way more energy to process and store protein than it does carbohydrate or fat–this is called the thermic effect of food. Essentially, one burns more energy dieting protein because it requires more energy for the body to process. In one study, twice as much energy was expended after meals on a high-protein diet versus a high carbohydrate, low-fat diet.1
Another study compared the effects of three diets differing in macronutrient (carb, fat, protein) composition on energy expenditure during weight loss maintenance. Weight loss causes resting energy expenditure (metabolic rate) to go down, which predisposes to weight regain. Results of the study showed that the very low-carb (and highest protein) diet had the LEAST effect on reducing resting energy expenditure following weight loss.2
The loss of energy as heat through the thermic effect of food is consistent with the second law of thermodynamics, which states that some energy is always lost in any chemical reaction. The idea that “a calorie is a calorie” defies this law.3
Hormonal changes associated with different types of food are also important. Diets high in carbs cause increased secretion of insulin, meaning elevated insulin levels, meaning more fat storage. Low insulin promotes fat burning.4,5
It seems obvious that the type of food consumed can affect energy expenditure and fat loss. Staying away from processed foods made with refined starches and added sugar is, “the road map to reducing the obesity epidemic in the United States,” said Dr. Dariush Mozaffarian, a cardiologist and dean of the Friedman School of Nutrition Science and Policy at Tufts University.
Food reward regions in the brain programmed much of this physical dependence on processed foods and refined starches. But the body can reverse it. Acute bouts of aerobic exercise have been shown to significantly suppress appetite and hunger while increasing satiety and fullness.6 Exercise in the form of resistance (weight) training can enhance insulin sensitivity,7 which results in reduced insulin secretion.8 Less insulin helps bodies favor fat burning over fat storage.
At its core, weight loss results from burning more calories than you consume. But the macronutrient composition of those calories is also vital. Different foods have substantially different metabolic and hormonal effects on the body. So what’s eaten (and how calories are expended) can change how much you eat and whether those calories are burned or stored.
Not all calories are created equal.