Composition Of Weight Lost During Short Term Weight Reduction. Metabolic Responses Of Obese Subjects To Starvation And Low Calorie Ketogenic And Nonketogenic Diets

This study compared three different approaches to weight loss in obese patients: complete fasting (starvation), an 800-calorie ketogenic diet (very low carb, high fat), and an 800-calorie balanced diet with normal proportions of carbs and fats. Six participants tried each approach for 10 days while researchers carefully measured what types of body weight they lost - water, fat, or muscle protein.

The results revealed an important distinction between total weight loss and fat loss. People on the ketogenic diet lost weight much faster (about 1 pound per day) compared to the balanced diet (about 0.6 pounds per day). However, this dramatic difference was almost entirely due to water loss, not fat loss. Both 800-calorie diets actually burned similar amounts of fat per day (about 165 grams), regardless of whether the calories came from carbs or fats. The ketogenic diet just caused the body to shed much more water weight.

The study also found that complete starvation led to the fastest weight loss but came with significant muscle protein loss - something neither of the 800-calorie diets caused to the same extent. Importantly, the participants' metabolic rates decreased in proportion to their total weight loss, regardless of which diet they followed.

This research helps explain why low-carb diets often show dramatic initial results on the scale, while highlighting that sustainable fat loss depends more on creating a calorie deficit than on the specific mix of macronutrients. In clinical practice, this knowledge helps set realistic expectations for patients and emphasizes focusing on long-term fat loss rather than rapid scale changes.