Ketogenic diets are superior for fat loss short term, but long term there are identical fat losses when calories are matched. Ketogenic diets don’t affect muscle strength but can result in reductions in performance for anaerobic exercise. Ketogenic diets maintain lean mass but few studies have found a ketogenic diet to be able to increase lean mass compared to a carbohydrate control diet.
THE PROS AND CONS OF GOING KETO FOR LOSING FAT KEY POINTS:
- Going keto for losing fat results in faster short term fat loss.
- Ketogenic diets are superior for short-term fat loss, but there are identical fat losses when calories are matched in the long term.
- Ketogenic diets don’t affect muscle strength but can result in reductions in performance for anaerobic exercise.
- Ketogenic diets maintain lean mass, but few studies have found a ketogenic diet to increase lean mass compared to a carbohydrate control diet.
INTRODUCTION TO KETO FOR LOSING FAT AND GAINING MUSCLE
There has never been a more controversial subject than keto diets and muscle loss. Ketogenic diets are characterized by high-fat and moderate to high protein content but of an insufficient level of carbohydrates (usually 20 g-50 g per day), thus forcing the body to primarily use fat as a fuel source. The ketogenic diet mimics metabolic starvation, resulting in large increases in the body’s use of fat as an energy source. The reduction of dietary carbohydrates decreases plasma insulin and increases glucagon; this state promotes liver glycogen breakdown and gluconeogenesis (i.e., creation of glucose from non-carbohydrate sources) and lipolysis of adipose tissue through the increase of HSL (hormone-sensitive lipase).(1)
This process of shifting from carbohydrates as a fuel source to fat is known as ketosis. Ketogenic diets increase the concentration of ketone bodies in the blood, usually above >0.5 mmol/L, indicating nutritional ketosis.(2) As the brain depends on glucose when following a ketogenic diet, the brain depends on ketone bodies as an energy source.(3) Ketone bodies are present under fed states; however, ketones increase with fasting, prolonged exercise, and reduced carbohydrate availability.
KETO FOR LOSING FAT STUDIES
Ketogenic diets are effective for weight loss by increasing satiety and reducing appetite. In a systemic review of the literature, the keto diet resulted in a negative energy balance of -339 kcals per day compared to a control diet.(4) A large number of studies in which subjects were not restricted by calories showed ketogenic diets resulted in lower calorie intake.(5, 6)
When calories are matched, there are no significant differences in losing body weight or body fat over a year.(7-9) Based on the evidence, ketogenic diets result in more weight loss short term; however, there are no differences in fat loss or bodyweight long term compared to a high carbohydrate, low-fat diets.(10) There is no evidence that a ketogenic diet is superior for fat loss to a high carbohydrate, low-fat diet in the long term when calories are equal.
KETO FOR LOSING FAT AND APPETITE
The decreases in appetite have been attributed to the high protein consumed on ketogenic diets and increased appetite-suppressing hormones (i.e., decreased leptin, ghrelin, etc.), resulting in a lower caloric intake. Others have suggested the increased fiber from consuming more vegetables also contributes to the reduced caloric intake. Thus, keto causes a substantial reduction in caloric intake compared to control diets.
Some have touted that ketogenic diets result in a “metabolic advantage” resulting in increased energy expenditure, but this was disproven by Kevin Hall. He showed that a ketogenic diet resulted in about a 100 kcal increase in energy expenditure after adjusting for body mass and composition.(11) The data from several studies suggest that the metabolic advantage of a ketogenic diet would be small, certainly not enough to make it superior to that of a carbohydrate-matched diet.