A Battle of Weight Loss Diet Schools: In-Depth Analysis of Traditional Low-Fat Diets and Low-Carbohydrate Models

Currently, there are two main types of weight loss diets: one is the traditional low-fat, energy-restricted diet, and the other is the low-carbohydrate diet that has become popular in industrialized countries in recent years. Advocates for these different diets each have their own arguments and perspectives. As medical professionals, it is necessary to have a deeper understanding of the effects and safety of these diets in order to help overweight and obese individuals make the right choices.

Traditional weight-loss diets emphasize that energy from carbohydrates should be the primary source of energy from the three macronutrients, and that energy intake should be reduced mainly by controlling fat intake. This is because each gram of fat produces 9 kilocalories of energy when burned in the body, more than twice the energy produced by the same amount of carbohydrates or protein. Furthermore, high-fat foods taste better, increasing appetite and leading to overeating and weight gain. For the same amount of energy provided, a high-carbohydrate diet carries a larger volume, creating a greater feeling of fullness in the stomach, which can signal the brain to stop eating.

This dietary structure is widely supported by authoritative institutions in my country and abroad. The *Dietary Guidelines for Chinese Residents* recommends that carbohydrates and fats provide 55%–65% and 20%–30% of total energy intake for adults, respectively. The *Guidelines for the Prevention and Control of Overweight and Obesity in Chinese Adults* suggests that carbohydrates, fats, and proteins should provide approximately 60%, 25%, and 15%–20% of total energy intake, respectively. For diabetic patients, the recommended therapeutic diet provides 55%–60% of energy from carbohydrates, less than 30% from fats, and 15%–20% from proteins.

Low-carbohydrate weight-loss diets are popular in Western industrialized countries, with the Atkins diet being a prime example in its early stages. Atkins, a cardiologist, first brought the relationship between insulin and weight loss to the public's attention in 1972. He believed that effectively controlling insulin secretion was key to weight loss. The core of his low-carbohydrate diet was to restrict only carbohydrate intake, while not limiting high-protein or high-fat foods.

Obese individuals can eat without limit during weight loss, indulging in delicious foods such as fish, poultry, meat, and eggs. This low-carbohydrate diet is implemented in several phases: for the first two to three weeks, daily carbohydrate intake should not exceed 20 grams. During this phase, rice, bread, potatoes, grains, fruits, and dairy products are strictly prohibited. In subsequent phases, as weight loss continues, carbohydrate intake can be gradually increased in small amounts.

The Atkins diet emphasizes controlling carbohydrate intake, with its energy sources primarily being fat and protein. Analysis shows that protein provides approximately 30% of the energy, while fat provides 50%–60%, with saturated fat contributing as much as 20%. This low-carbohydrate diet does indeed have a rapid weight-loss effect in the short term, and since it doesn't restrict food intake and allows for unlimited meat consumption, it is popular among many obese individuals.

The theoretical basis for this includes: carbohydrates are absorbed and converted into blood sugar, which stimulates insulin secretion. Insulin is an anabolic hormone that carries glucose into cells to synthesize fat and prevents the burning and breakdown of body fat. Therefore, reducing carbohydrate intake reduces the stimulation of insulin secretion, which is beneficial for the breakdown of body fat and weight loss. Reducing the proportion of energy supplied by carbohydrates may correspondingly increase the proportion of energy supplied by protein. Dietary protein has the effect of suppressing appetite, thereby reducing energy intake. At the same time, food protein has a strong thermic effect, increasing the dissipation of body heat, and therefore increasing energy expenditure.

Although these diets advocate different proportions of energy from the three macronutrients, they all aim to accelerate weight loss by reducing the proportion of energy supplied by carbohydrates in the diet.