Intermittent fasting makes no significant difference to weight loss compared with a normal diet, a study has revealed.
Scientists at John Hopkins University randomly assigned 41 adults with obesity and prediabetes to either intermittent fasting with a 10-hour eating window or a regular eating pattern for 12 weeks to compare weight loss.
Participants in both arms received prepared meals with the same nutrients and instructions on when to consume the meals.
Researchers found that after 12 weeks, both groups lost about the same amount of weight and there were no real differences in fasting glucose, waist circumference or blood pressure.
The study's authors said the findings suggest that fasting only induces weight loss due to a reduction in calories, but that it remains useful as a weight loss technique as it allows patients to consume familiar foods. It is also beneficial for patients who do not wish to count calories.
Previous evidence has shown that when adults with obesity limit their eating window to four to ten hours, they naturally reduce caloric intake by approximately 200-550 calories per day.
Intermittent fasting, also known as time-restricted eating, is a diet approach where patients limit their eating to a window of time during the day and then fast for the remaining hours.
Earlier this year, Prime Minister Rishi Sunak revealed that he fasts for 36 hours a week and consumes nothing but black coffee, tea and water between 5pm every Sunday until 5am on Tuesday morning.
There are varying types of fasting, some including reducing calorie intake significantly on certain days, or going without food entirely on some.
Those who want to try it are advised to speak to medics first, and it is not advised for people with a history of disordered eating or who are pregnant.
A study published by Queen Mary University earlier this year found that fasting for three days could trigger weight loss but that going without food for a week carried no significant further health benefits.
Scientists monitored 12 healthy volunteers taking part in a week-long water fast and tracked changes in the levels of 3,000 proteins in their blood.
They observed that one in three of the proteins measured changed “significantly” in all major organs, including changes in proteins that make up supportive structures in the brain.
The volunteers lost an average of 5.7kg of both fat mass and lean mass during the fast. After three days of eating after the fast, the weight stayed off but the health benefits of fasting only extended to three days of calorie restriction, the study found.
