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 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.
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.
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.
Keto and Weight Loss
It almost sounds counterintuitive at first; can a high-fat diet promote weight loss?
A review of 13 randomized controlled trials (1,415 patients) found that people on the ketogenic diet lost significantly more weight than people on low-fat diets. They also kept the weight off for 12 months or more. While the diets in these studies contained no more than 50 grams of carbohydrate (a typical keto diet plan), low-carb diets with more generous amounts of carbohydrate (≥ 120 gm/day) showed similar results (more weight loss with low-carb than low-fat) in a review of 17 randomized controlled trials.
How is the keto diet so effective at promoting major weight loss?
There are two theories.
1. Metabolic Advantage
According to one hypothesis, low-carb diets have a distinct “metabolic advantage” over diets with higher carbohydrate content when the number of calories consumed are the same. This metabolic advantage is essentially an increase in the expenditure of energy (calories) on the low-carb diet.
2. Appetite Suppression
A common symptom of the ketogenic diet is appetite suppression. This feeling of fullness associated with the state of nutritional ketosis may be linked to a higher intake of protein and fat.
Should you count calories on keto?
It’s more about the type of calories than the amount.
But, counting calories does have some benefits. It may be useful on keto for people who are still not getting results. These individuals may be unknowingly consuming too many fats, such as coconut oil, in order to increase ketones. Tracking calories may offer a reality check on what normal portion sizes look like.
Body weight is self-regulated on the keto diet by emphasizing the types of food over quantity of food consumed. This is the best approach to reducing obesity, as well as related disorders such as diabetes and cardiovascular diseases.