Researchers from the University of Illinois at Chicago found that water fasting can help you lose weight and improve your metabolic health (lower blood pressure and blood cholesterol levels), but both weight and performance return to normal shortly after the fast ends. Research published in the journal Nutrition Reviews.
Researchers analyzed data from eight water fasting studies. With this type of diet, people consume only small amounts of juice and soup. The authors found that fasting led to noticeable short-term weight loss. Those who fasted for five days lost 4% to 6% of their weight, between days seven and 10, 2% to 10%, and between days 15 and 20, 7% to 10%.
Three studies tracked whether participants regained the weight they lost after the fast was over. In one, people completely regained the weight they lost during the five-day fast in three months. In the other two studies, there was less return to normal weight as participants tried to maintain a calorie deficit after fasting.
However, the drop in blood pressure, cholesterol, and blood sugar was short-lived and quickly rebounded after participants resumed eating. Additionally, 75% weight loss during fasting was associated with a loss of muscle mass, not fat.
The most common side effects of fasting included headache, insomnia, and feelings of hunger. Serious side effects such as metabolic acidosis or death were not reported in the studies. However, the authors stressed that no one should fast for more than five days without medical supervision.
The authors of the previous study to solvethat intermittent fasting or counting calories may be safer and more effective ways to lose weight.