Long-term vs. Short-term: Nutritional experiments reveal the true effects and health risks of two types of weight-loss diets.

We will conduct an experimental study to compare two types of weight-loss diets. According to the results of a large-scale nutrition survey in China in 2002, dietary structure is closely related to the occurrence of overweight and obesity. People whose energy intake from carbohydrates is between 55% and 65% are 8% less likely to be overweight/obese than those whose carbohydrate energy intake is below 55%; those whose carbohydrate energy intake is 65% or higher are 31% less likely to be overweight/obese. As the percentage of energy supplied by dietary fat increases, the number of overweight and obese individuals increases significantly.

Results from randomized controlled trials in developed countries, however, indicate that increasing the proportion of total fat in the diet leads to greater weight loss in obese individuals. Why these two different results? The surveys in my country were conducted among the general population, while the subjects in industrialized countries were mostly obese individuals. Experts point out that the appropriate proportion of macronutrients for energy supply differs between people of normal weight and obese individuals because many obese patients have insulin resistance, making diets with lower carbohydrate energy intake more beneficial for them.

According to existing literature, most studies indicate that low-carbohydrate diets lead to significant weight loss in short-term trials. However, this advantage of rapid weight loss with low-carbohydrate diets disappears in long-term studies. The relationship between the energy source of weight-loss diets and human health also needs to be evaluated. Early low-carbohydrate diets proposed by Atkins, because they did not restrict energy or meat, resulted in excessive intake of saturated fatty acids, increasing the risk of cardiovascular disease. Even if such diets can lead to rapid weight loss, they are not recommended.

Recent studies have shown that the type of dietary fatty acids has a greater impact on health than the proportion of total fat providing energy. For example, replacing some carbohydrates in the diet with monounsaturated fatty acids can increase high-density lipoprotein cholesterol. These examples demonstrate that while the proportion of energy provided by fat differs in the two situations, it is not the decisive factor in improving blood lipid levels. Appropriately increasing protein intake in a weight-loss diet to replace some carbohydrates can lead to greater body fat loss and the retention of more lean body tissue.

Foreign literature reports that the incidence of stroke in some Asian countries is much higher than in Europe and the United States, which is attributed to the low intake of animal protein in these countries. However, numerous studies have shown that significantly increasing dietary protein intake can lead to a significant increase in urinary calcium excretion. Clinically, protein intake is restricted for patients with kidney disease, as it can worsen their symptoms. All of this indicates that excessive protein intake may have negative health effects. Based on current research, it is insufficient to determine the maximum limit for protein intake.

The three macronutrients are the body's energy sources and can be substituted for each other to a certain extent. At a given energy level, increasing the proportion of energy provided by one nutrient will inevitably reduce the proportion of energy provided by one or two other nutrients. From a long-term health perspective, it is undesirable for any energy-providing nutrient to be too high or too low, but some adjustments can be made within a certain range based on individual circumstances and past dietary habits. The closer the structure and types of food in a weight-loss diet are to the past dietary habits of overweight or obese individuals, the better the results, enabling patients to maintain the diet for life after achieving a certain weight loss effect.

For those following a weight-loss diet, the proportion of energy derived from protein should be appropriately increased. Increasing the energy provided by protein in the diet is more conducive to weight loss, ensuring that the weight lost primarily comes from body fat tissue while better preserving lean body tissue. This is especially important for obese middle-aged and elderly individuals with low activity levels; insufficient protein intake can prevent the proper maintenance of muscle tissue after weight loss.