Analysis of starvation and ultra-low-calorie diets for severe obesity

Fasting Therapy:

Fasting therapy, also known as fasting, is one of the earliest methods of weight loss through dietary control. As early as 1959, Bilom pointed out that short-term fasting was effective in treating obesity. Reports indicate that 107 obese individuals fasted for 5-14 days, followed by 1-2 days of intermittent fasting. The results showed that 40% initially lost weight but then regained it; 43% maintained their weight; and only 17% experienced weight loss.

Fasting therapy requires strict adherence to indications. Patients with severe obesity but no comorbidities must be carefully selected, along with those willing to cooperate and eager to achieve results. The treatment course is generally 10-14 days and should not be too long. Patients will feel hungry in the first 1-2 days, and mild ketosis will occur within 3-4 days, after which the feeling of hunger will gradually disappear. They may experience fatigue, weakness, low blood pressure, and are particularly prone to orthostatic hypotension. Occasionally, arrhythmia and increased urination may occur. Weight loss begins, occurring rapidly in the first few days, typically exceeding 0.5 kg per day. This method is a short-term therapy with definite efficacy. A low-calorie diet must be maintained and consolidated to preserve the therapeutic effect. This method has certain effects on the body and is generally not recommended.

Although fasting therapy has definite short-term weight loss effects, its contraindications should be noted during implementation. Common contraindications include: ① Stenotic vascular diseases (angina pectoris, carotid artery stenosis), history of myocardial infarction, cerebral hemorrhage. ② Kidney dysfunction. ③ Liver disease (except mild fatty liver), porphyria, anemia. ④ Gout, hyperuricemia. ⑤ Wasting diseases (acute and chronic diseases, fever, negative nitrogen balance, malignant tumors). ⑥ Juvenile type 2 diabetes. ⑦ Pregnancy. ⑧ Mental disorders (the "bulimia stage" of anorexia nervosa).

Ultra-low energy diet: Complete fasting has many contraindications, and enduring the pain of hunger is difficult for most people to accept; therefore, the ultra-low energy diet was developed. This method controls daily calorie intake to around 2500 kJ. This diet contains high-biological-value protein and is often used for severely obese and morbidly obese patients, aiming for rapid weight loss. Simultaneously, it preserves the body's non-fat components by utilizing the protein and carbohydrates in the diet. This liquid diet was popular in the mid-1970s, but due to frequent adverse effects, it is now less commonly used.

Later, a modified ultra-low-energy diet was developed, containing high-biological-value protein, a small amount of carbohydrates, and a minimum amount of essential fatty acids, minerals, and vitamins. This is called the "protein-saving modified diet," providing 1.5g of protein per kilogram of body weight daily. There is also a "liquid formula diet" that provides approximately 33-70g of protein daily. The former diet does not contain any carbohydrates and only allows lean meat, fish, and poultry. The sole source of fat is also from these foods. The liquid diet is based on milk or eggs. In addition to protein, 30-46g of sugar and approximately 2g of fat can be added. Both diets require supplementation with vitamins and minerals. The results of both diets are similar; studies of over 1000 patients have demonstrated that ultra-low-energy diets can significantly reduce weight, and this reduction is directly proportional to the duration of treatment. Weight loss can reach 20kg within 12 weeks. It is important to note that to prevent kidney damage and avoid a significant increase in blood ketone bodies, 1.5-3L of water must be consumed daily.

Suitable patients for ultra-low-energy diet therapy are: individuals aged 20-60 years with a high to severe obesity rate of 60% or more. For refractory obesity that has not achieved therapeutic goals with previous treatments, treatment for more than 3 months is required. A comprehensive physical examination is necessary before treatment to rule out contraindications: acute myocardial infarction, cerebrovascular disease, cancer, type 1 diabetes, liver and kidney disease, mental illness, and pregnancy. If the patient has type 2 diabetes, insulin treatment must be discontinued.

While the effects of ultra-low-energy diets are significant, patients often cannot maintain their normal weight, meaning the effects are not consolidated. One report states that after 22 months, 56% regained their pre-obese weight.