An investigation was conducted to study the changes in body weight and blood lipids during Ramadan fasting in men on hypocaloric diets. Sixteen healthy male college students were fed a high-carbohydrate diet for the first 2 wk (means 1696 kcal/d), followed by another 2 wk of high-fat diet (means 1834 kcal/d). Fasting blood samples were taken on days 0 (base line), 14, and 28 and were analyzed for triglycerides (TGs) and cholesterol. By the end of Ramadan, body weight, blood TGs, and high-density lipoprotein cholesterol (HDL-chol) had decreased significantly (p less than 0.05), low-density lipoprotein cholesterol (LDL-chol) had increased, and total cholesterol had not changed compared with base-line values. The variance in blood lipid levels was explained by weight change through linear and curvilinear regression models. The findings contribute to a better understanding of the contrasting results reported by various investigators and they may be useful in regulating blood lipid levels through Ramadan fasting.