Energy balance: interpretation of data from rural China

Data used for this analysis are pertinent to the issue of energy balance and body-weight control. They were obtained, in a comprehensive study of human diet, lifestyle, and disease mortality, from 65 counties (130 villages, 6500 adults) of rural China (Chen et al., 1990). After adjusting the food intake data to represent a reference male adult involved in the least physical activity and representing the same body weight, total calorie intake (40.6 kcal/kg body weight) was about 30% higher in China when compared with an average adult American male (30.6 kcal/kg bw). However, the body mass index for the Chinese male was about 25% lower (20.5 vs. 25.8 kg bw/m2). Diets in rural China were low in fat (14.5% of energy), relatively low in protein (65.8 g/day), and high in fiber (33 g/day), representing a diet unusually rich in plant-based foods (e.g., including about 90% of the total protein). It is believed that the excess energy intake among the Chinese is mostly attributed to their greater physical activity. However, some unknown but significant, and probably difficult to measure, amount could be due to increased energy expenditure associated with non-post-prandial basal metabolism. This hypothesis is based, in part, on evidence from experimental animal data from this and other laboratories showing that laboratory rats fed diets comprised of substantially reduced intakes of protein consume more energy, but gain less weight. They also exhibit increased thermogenesis, due both to enhanced metabolic body heat and to diet-driven physical activity, while sharply reducing blood cholesterol concentrations and tumor development.