What Accelerates the Deterioration of Whole–Life Cycle Events in Type 2 Diabetes: Too Much Dietary Fat or Carbohydrates

Diabetes is a chronic, lifelong metabolic disorder characterized by elevated blood glucose levels. The role of diet and nutrition in the entire life cycle of metabolic diseases, particularly type 2 diabetes (T2D), is pivotal and represents the primary modifiable factors in combating the onset and progression of diabetes. The previous association between a high-sugar diet and diabetes risk has been well established. However, there is now evidence suggesting that a shift towards reduced carbohydrate intake and increased dietary fat may be linked to higher morbidity and mortality rates in patients with diabetes. This review investigated the effects of dietary fats and carbohydrates on the onset and progression of T2D and its associated complications (microvascular and macrovascular) and fatal events by reviewing several clinical studies and animal experiments. A lack of controlled trials comparing high-sugar and high-fat diets (HFDs) in clinical studies hinders us from drawing consistent conclusions. The majority of animal studies demonstrated a greater impact from HFDs compared with higher-sugar diets. There are several diets for treating diabetes that restrict fat intake below the upper limit of the dietary guidelines, and people with diabetes or abnormal glucose tolerance seem more able to tolerate low-fat, high-carbohydrate, low-calorie diets. Due to various factors, including the types of carbohydrates and fats, caloric intake, cognition, population age, and study design, it is difficult to conclusively determine which ratio of dietary components is more likely to contribute to diabetes, microvascular and macrovascular complications, or mortality events. Animal experiments may provide a systematic approach for simulating the effects of dietary fats and carbohydrates across the entire diabetes life cycle. Nevertheless, care must be taken when generalizing the findings from animal models to human contexts. Consequently, there is still a need for more high-quality, large, prospective controlled research to elucidate the role of dietary structure with different fat to carbohydrate ratios across the life cycle of diabetes. Meanwhile, studies should analyze relevant interactions, including potential effect modification factors.