To be specific, malnutrition caused by low-protein diets can reduce the expression of insulin-like growth factor 1 (IGF-1), suppress the absorption of intestinal calcium and phosphorus, and inhibit bone calcification (Muñoz and Argente, 2002); exercise can regulate the biological activity of osteoblasts, increase mass accumulation of bone, and prolong bone turnover rate; furthermore, long-term plus regular weight-bearing exercise can increase BMD and reduce bone loss (Stein and Shane, 2003) (Figure 1). The gene discussed is IGF1; the disease is malnutrition.