According to a recent analysis all forms of fasting reviewed produced mild to moderate weight loss, 1%-8% from baseline weight, which represents results that are similar to that of more traditional, calorie-restrictive diets. Intermittent fasting regimens may also benefit health by decreasing blood pressure and insulin resistance, and in some cases, cholesterol and triglyceride levels are also lowered. Other health benefits, such as improved appetite regulation and positive changes in the gut microbiome, have also been demonstrated.
The review looked at three types of intermittent fasting:
- Alternate day fasting, which typically involves a feast day alternated with a fast day where 500 calories are consumed in one meal.
- 5:2 diet, a modified version of alternate day fasting that involves five feast days and two fast days per week.
- Time-restricted eating, which confines eating to a specified number of hours per day, usually four to 10 hours, with no calorie restrictions during the eating period.
Studies showed alternate day fasting resulted in weight loss of 3%-8% of body weight over three to eight weeks, with results peaking at 12 weeks. Individuals on alternate day fasting typically do not overeat or binge on feast days, which results in mild to moderate weight loss, according to the review.
Studies for the 5:2 diet showed similar results to alternate day fasting, which surprised the study’s reviewers. The subjects who participate in the 5:2 diet fast much less frequently than alternate-day fasting participants do, but the results of weight loss results are similar.
Weight loss in both the alternate day and 5:2 fasting are comparable to more traditional daily calorie-restrictive diets. And, both fasting diets showed individuals were able to maintain an average of 7% weight loss for a year.
There are a number of practical considerations for those who may want to try intermittent fasting. Among the considerations are:
- Adjustment time — Side effects such as headaches, dizziness and constipation subside after one to two weeks of fasting. Increased water intake can help alleviate headaches caused by dehydration during this time.
- Exercise — Moderate to high-intensity endurance or resistance training during food abstention can be done, and some study participants reported having more energy on fast days. However, studies recommend those following alternate day fasting eat their fasting day meal after exercise.
- Diet during fasting — There are no specific recommendations for food consumption during intermittent fasting, but eating fruits, vegetables and whole grains can help boost fiber intake and help relieve constipation that sometimes accompanies fasting.
- Alcohol and caffeine — For those using an alternate day or 5:2 fasting plan, alcohol is not recommended on fast days as the limited calories should be used on healthy foods that provide nutrition.
People love intermittent fasting because it’s easy. People need to find diets that they can stick to long term. It’s definitely effective for weight loss and it’s gained popularity because there are no special foods or apps necessary. You can also combine it with other diets, like Keto.