Medical definition of a low-energy balanced diet: theoretical models, evidence for fat loss, and nutritional ratio recommendations

I. Definition of a Calorie-Restricted Balanced Diet A calorie-restricted diet (CRD) is a dietary pattern that restricts energy intake while ensuring basic nutritional needs are met. The proportion of macronutrients supplied by the diet should meet the requirements of a balanced diet. CRD has a clear intervention effect on prolonging life and delaying the occurrence of age-related diseases. There are currently three main types of CRD: 1. A low-energy diet pattern that, while meeting the five macronutrient requirements (protein, vitamins, minerals, dietary fiber, and water), appropriately reduces the intake of fat and carbohydrates, subtracting 30%-50% of the energy from normal free-eating intake. This usually needs to be done under the supervision of a doctor. 2. Reducing daily intake by approximately 500 kcal from the target intake. 3. Daily energy intake of 1000-1500 kcal. II. Implementation and Evidence of Calorie-Restricted Balanced Diets

Evidence suggests that a 6-month CRD intervention (25% reduction in energy intake) in overweight individuals significantly improved insulin sensitivity compared to non-CRD participants, which was attributed to weight loss. A study assessing the impact of CRD-induced weight loss on visceral fat in adults confirmed that a 12-week CRD intervention (CRD target: 25 kcal/kg, baseline energy intake approximately 30 kcal/kg) effectively reduced body weight, adipose tissue weight, visceral fat area, and the risk of atherosclerosis in adults with visceral fat area ≥100 cm². Multiple studies have confirmed that the proportion of energy derived from fat in CRD should be consistent with a normal diet (20%-30%); both excessively low and high levels can lead to dietary imbalances. Studies supplementing obese individuals with marine fish or fish oil preparations have reported that n-3 polyunsaturated fatty acids (n-3 PUFAs) significantly improve arterial elasticity, systolic blood pressure, heart rate, blood triglycerides, and inflammatory markers, thus enhancing the weight loss effect of CRD. In a randomized controlled trial examining bone mineral density under high-protein and normal-protein intake levels during an energy-restricted diet, 47 postmenopausal women were randomly assigned to a high-protein diet group (HP, 24%) and a normal-protein diet group (NP, 18%), with fat intake at 28% and calcium intake controlled at 1.2 g/day. After one year, compared to the NP group, the HP group showed reduced bone mineral density loss in the lumbar spine, distal radius, entire hip joint, and tibial trabeculae. Since CRD reduces total energy intake, it inevitably leads to a decrease in the intake of thermogenic macronutrients. The proportion of protein intake should be appropriately increased (1.2-1.5 g/kg, or 15%-20%) to maintain nitrogen balance during weight loss, while also reducing the risk of cardiovascular disease and increasing bone mineral content. The weight loss effect of different protein sources may vary; studies have found that soy protein is superior to casein in fat loss, and its effect on lowering total cholesterol and LDL cholesterol in the blood is also more significant. Carbohydrate intake should be determined based on protein and fat intake (40%-55%). Too much or too little carbohydrate intake will lead to dietary imbalance. Carbohydrate sources should follow relevant dietary guidelines, primarily consisting of complex starches, ensuring an intake of 25-30 g/day of dietary fiber. Strictly limit the intake of simple sugars (monosaccharides and disaccharides) in foods and beverages. Obesity is associated with metabolic abnormalities of certain micronutrients, especially deficiencies in calcium, iron, zinc, vitamin A, vitamin D, and folic acid. Obesity and dietary weight loss can also cause bone loss. A meta-analysis showed that obese individuals have a 35% higher risk of vitamin D deficiency than normal-weight individuals and a 24% higher risk than overweight individuals. Supplementing with vitamin D and calcium during weight loss interventions can enhance weight loss effects. A study evaluating the relationship between visceral fat reduction and blood pressure changes in overweight or obese individuals during a 12-week meal replacement weight loss intervention showed a significant positive correlation between visceral fat reduction and improvements in systolic and diastolic blood pressure in overweight and obese male volunteers, confirming that visceral fat reduction during weight loss plays a crucial role in improving related health outcomes.

Recommendations for the Application of Energy-Restricted Balanced Diets: Recent studies suggest that nutritional interventions and meal replacements can achieve both weight loss and nutritional balance. In addition to energy restriction, CRD also recommends nutritional balance. Specific recommendations are as follows: (1) CRD can reduce weight and lower fat content. (2) Ensuring adequate protein intake (1.2~1.5g/kg) may enhance the weight loss effect of CRD. (3) Replacing some casein with soy protein can enhance the weight loss effect of CRD. (4) The proportion of fat energy in CRD should be 20%~30%. (5) Appropriately increasing foods rich in n-3 polyunsaturated fatty acids or supplementing with fish oil preparations can enhance the weight loss effect of CRD. (6) The proportion of carbohydrate energy in CRD should be 40%~55%. (7) Increasing the intake of vegetables, fruits, oats, and other foods rich in dietary fiber can enhance the weight loss effect of CRD. (8) Appropriate supplementation with vitamin D preparations and calcium can enhance the weight loss effect of CRD. (9) CRD using a nutritional meal replacement model is more helpful in losing weight.