Fasting-Mimicking Diet Shows Health Gains—but Carries Serious Risks

A short-term eating plan known as the fasting-mimicking diet has drawn attention for its potential health effects. Designed to copy some benefits of fasting, it involves severe calorie restriction over five days. Research suggests it may improve weight, blood sugar control, and inflammation—but experts warn of risks if misused.

The diet works by sharply cutting calories for a limited time. On the first day, participants eat around 1,000 to 1,100 calories, dropping to 700 to 900 calories for the next four days. Studies show this approach can lead to short-term reductions in weight, waist size, and blood sugar markers like HbA1c.

A 2017 trial by Wei et al., published in *Science Translational Medicine*, tested three monthly cycles of the diet on healthy adults. Results included better insulin sensitivity, lower trunk fat, and improved HbA1c levels. A 2021 follow-up in *Nature Communications* confirmed these benefits lasted up to six months. However, the diet is not without side effects. Participants often report hunger, fatigue, irritability, and headaches. Poor hydration can worsen these issues, sometimes causing dizziness or circulation problems. Repeating the diet too frequently without proper planning may also lead to nutrient shortages. Experts stress that this method is only suitable for healthy adults in short bursts—not as a long-term eating pattern. Those with diabetes should only try it under medical guidance. Current evidence does not prove it works better than traditional, balanced diets for sustained health improvements.

The fasting-mimicking diet may offer temporary benefits for weight, blood sugar, and inflammation. But its strict calorie limits and possible side effects mean it is not for everyone. Proper supervision and careful planning remain essential for anyone considering this approach.