Background/objectives: Changes in food consumption patterns during Ramadan may cause metabolic changes, but these have not been well studied. We aimed to determine food intake, glucose homeostasis, lipid profiles, and body composition before, during, and after Ramadan fasting.

Methods: 160 healthy men were enrolled and investigated at three times (before, at the end of, and 1 month after Ramadan). Body composition was estimated by bio-impedance. Fasting blood samples were obtained for measuring fasting blood sugar (FBS), lipid profiles and insulin level. Insulin resistance (IR) was identified by the homeostatic model assessment (HOMA) of peripheral IR. Food intake was measured using a validated food frequency questionnaire before and during Ramadan. Statistical analysis was performed by SPSS 16 and P < 0.05 considered the level of significance.

Results: Anthropometric parameters such as body weight, body mass index, and body fat percentage (BFP) as well as FBS and circulating triglycerides were all decreased significantly at the end of Ramadan compared with the same indices measured prior to Ramadan (all P < 0.001). In contrast, at the end of Ramadan, HOMA-IR was significantly elevated (P < 0.001). One month after Ramadan, these traits had all started to return to their pre-Ramadan levels, but were still disrupted. Food intake of all food groups except carbohydrates were decreased during Ramadan.

Conclusion: Ramadan fasting may lead to both positive and negative health effects such as a decrease in FBS, weight, BFP, and increase in LDL and IR in healthy adults. However, these effects were all transitory.