This study investigated whether Greek Orthodox Christian fasting during Holy Week can change body composition and cardiometabolic parameters in overweight individuals, and whether these changes are maintained one week after fasting cessation (FC). Body composition and physiological and biochemical parameters were measured before, immediately after (n = 23) and one week after FC (subgroup of n = 10). Fasting resulted in decreased body weight, waist circumference, waist-to-hip ratio, body mass index and total body fat, as well as blood glucose, total cholesterol and low-density lipoprotein cholesterol levels. Nutrition analysis showed a decreased protein and saturated fat intake during fasting. FC (n = 10) resulted in a decreased carbohydrate intake and increased protein and cholesterol intake compared to fasting. Fasting resulted in decreased blood glucose, total cholesterol and LDL cholesterol levels but returned to pre-fasting levels after FC. Greek Orthodox Christian fasting during Holy Week is beneficial for body composition and some aspects of cardiometabolic health. However, these favourable changes are not maintained one week following fasting.