The Optimal Dietary Fat to Carbohydrate Ratio to Prevent Obesity in the Japanese Population: A Review of the Epidemiological, Physiological and Molecular Evidence

Abstract

Summary The prevention of obesity, which leads to diabetes and other diseases, is a major concern for public health. There might be an optimal dietary fat to carbohydrate ratio for prevention and treatment of obesity. According to the Japanese Dietary Reference Intakes (RDA) for 2010, the optimal fat intake is 20-30% of energy for ages 1-29 y and 20-25% for ages 30 y and over. Upper boundary values of this recommendation were the median of the percentage of energy from dietary fat in Japanese. In a systematic review to estimate the optimal dietary fat to carbohydrate ratio, it was found that obese subjects with hyperinsulinemia (or insulin resistance) lost more weight on a mild low-carbohydrate (LC) (or low-glycemic load diet; 40% carbohydrate, 30-35% fat) than on a low-fat (LF) diet (55-60% carbohydrate, 20% fat), whereas those without hyperinsulinemia showed the opposite. In non-obese primarily insulin-sensitive subjects, decreasing fat rather than carbohydrate intake is generally more effective to prevent obesity. Physiological and molecular evidence supports this conclusion. Increased carbohydrate intake, especially in high-glycemic food, leads to postprandial hyperglycemia and hyperinsulinemia, which are exaggerated in obese insulin-resistant subjects. Even in an insulin-resistant state, insulin is able to stimulate fatty acid synthesis in liver, activate lipoprotein lipase, and prevent lipolysis in adipose tissues, which all facilitate adipose tissue enlargement. Optimal dietary fat to carbohydrate ratio may differ in populations depending on their prevalence for obesity. Because the prevalence of overweight/obesity in Japanese is low, a LF diet is recommended in the general population. Key Words low-carbohydrate diet, low-fat diet, RDA, insulin resistance, obesity , as compared with women who had a BMI of less than 23.0 kg/m 2 ( 2 ). In Japan, the prevalence of overweight/obesity (BMI Ն 25 kg/m 2 ) in adults is very low compared with the United States: 30.4% in men and 20.2% in women in 2007, according to Japanese cross-sectional nationwide surveys ( 3 ). However, a strong positive association between baseline BMI and the incidence of diabetes in the follow-up period was observed similar to that in the United States. In a Japanese cohort of healthy men ( n ϭ 16,829) and women ( n ϭ 8,370) followed for 7.4 y, new cases of diabetes were documented in 869 men and 224 women ( 4 ). The relative risk of diabetes was 5.55 for men with a BMI of 25.2 to 26.3, compared with men who had a BMI of 15.0 to 19.7, and the relative risk of diabetes was 5.70 for women with a BMI of 24.4 to 25.9, compared with women who had a BMI of 14.9 to 19.1. Therefore, in Japan also, the prevention of overweight/obese subjects is a major public issue.The role of dietary fat and carbohydrate in the obesity epidemic has been a hotly debated topic for decades and remains unresolved. To reduce the incidence of obesity in general populations, public statements on optimal ratios of dietary fat to carbohydrate have been issued. Health organiz...

Periodontal disease and percentage of calories from fat using national data

“…The percentage of calories from fat is the percentage of total caloric intake that comes from calories in fat, and in Japan this is used as an index for dietary intake standards . In addition, many studies have examined the association between fat and carbohydrates, comparing low‐fat, high‐carbohydrate diets with high‐fat, low‐carbohydrate diets.…”