People have started to put ketogenic diets above all other types of weight loss and sports diets. But most of the misunderstanding comes from conflating the effects of ketogenic diets on weight loss, therapy for selected diseases, and athletic performance. What's the real story with ketogenic diets?
The effect of ketogenic diets on weight loss and fat burning is not superior to other weight loss diets with the same amount of energy and especially protein, which are responsible for satiety and increased thermogenesis. While ketogenic diets do indeed have a higher initial weight loss in the first 2 weeks of the diet (by reducing glycogen stores and bound water), within 4 weeks the results for both weight loss and fat reduction are the same as (or worse than) e.g. HCLF (high carb, low fat) diets.
"Keto-adaptation" does indeed increase the oxidation (burning) of fats in the body, but with higher fat intake in the diet, more fat is stored in the body! In other words, ketogenic diet does indeed increase lipolysis, but it also increases lipogenesis in the body, and ketosis alone does not lead to an overall decrease in fat balance! (Yes, as long as you are not in an energy deficit, you can still gain new fat in ketosis).
Ketogenic diets are of importance in the THERAPY of selected diseases such as morbid obesity, diabetes, epilepsy and others, but it is a well-defined clinical nutrition. At the same time, they may be more suitable for weight reduction without the possibility of increasing energy expenditure by physical activities (e.g. In the case of morbidly obese persons, the strict elimination of carbohydrates results in a greater decrease in energy intake with unrestricted consumption of fatty foods than with strict elimination of fat and unrestricted consumption of carbohydrate foods and sweetened beverages. Conversely, "classic" HCLF diets result in greater increases in energy expenditure through exercise and may be more appropriate for the general population with overweight, first-degree obesity, and recreational athletes.
Ketogenic diets have a negative effect in most sports where SPORTS PERFORMANCE depends on glycogen (including most endurance sports) - oxygen consumption increases to maintain the same performance (e. g. cycling, sports walking) and the RATE OF ATP (adenosine triphosphate) RESYNTHESIS during exercise is significantly lower from fat metabolism (0.4 mol ATP/min) than from aerobic and anaerobic glycogen breakdown (1-2 mol ATP/min). The high proportion of fat in the diet on a ketogenic diet slows the absorption of both protein and carbohydrate and delays recovery. In addition, fats are not usable as a ready source of energy directly during exercise (with the exception of MCTs). Thus, ketogenic diets may be appropriate in sports such as weightlifting or power triathlon, but some athletes may struggle with adequate protein intake (protein intakes higher than about 1.5 g/kg can disrupt ketosis).
In summary, ketogenic diets MAY be suitable for sports where performance is independent of glycogen (weightlifting, power triathlon) or extreme endurance performance (ironman races, ultramarathon), for patients with diabetes, morbid obesity and also for people who need to lose weight without the possibility of increasing their energy expenditure through movement (e.g. post hip replacement). Conversely, "classic" high-carb low-fat (HCLF) diets are more appropriate for sports where performance is glycogen-dependent (i. e. the vast majority of sports from biathlon, to cycling and team sports, to bodybuilding and CrossFit) and for recreational athletes and overweight and moderately obese individuals who want to lose weight in the context of increased physical activity.
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