Several recent research papers have found that time-restricted eating can help to prevent diabetes and heart attacks and prolong life (Cell Metabolism, Oct 4, 2022;34(10):1442-1456). However, some people express concern that athletes and regular exercisers may develop low blood sugar and lose muscle if they go on a schedule of not eating for intermittent periods such as 6PM to 6AM. An exciting study now shows that time-restricted eating can improve health in serious athletes and may even help them to improve running performance by helping them to lose excess body fat (Nutrients, Feb 2023;15(4):985).
• Fifteen dedicated runners ate their normal diet for four weeks and then had many tests, followed by four more weeks on their regular diet.
• Then they went on a time-restricted diet of eating regularly for eight hours starting in the morning, followed by 16 hours of eating no foods whatever until the next morning.
There was no difference between the two study periods in the amount of calories they burned per day at rest, calories eaten per day, blood pressure, blood insulin, sugar or cholesterol levels, and markers of insulin resistance. However, their body composition changed significantly after the period of restricted eating. They lost more body fat, fat in their legs, and percent body fat, with no loss of muscle. This study showed that the 16-hour fasting pattern had no adverse side effects and could improve performance by helping them lose excess body fat. Another study on weight lifters found the same results: loss of body fat and no loss of muscle (J Transl Med, 2016;14:290).
Obesity and Time-Restricted Eating
Time-restricted eating also improved the health of older obese men and women. Older obese people are at high risk for heart attacks, diabetes, and premature death (Vasc Health Risk Manag, 2019; 15: 89–100). A six-week study of men and women aged 65-74 found that both sexes lost significant weight and men lost more belly fat by fasting for 16 hours per day, from 8PM to 12 noon (Experimental Gerontology, Apr 2023;174:112116). Furthermore, there was no loss of muscle size since time-restricted eating did not impair rates of muscle protein synthesis. Another study of time-restricted eating found that when diabetics ate only from 8AM to 6PM, they were able to reduce their doses of medications to control their high cholesterol and high blood pressure (Cell Metabolism, Dec 5, 2019).
Fasting Periods Should Be At Night, Not During The Day
A review of seven scientific studies showed that moving around after you eat reduces the after-eating rise in blood sugar (Sports Med, Aug 2022;52(8):1765-1787). Lying down and not moving after eating caused a higher rise in blood sugar (Topics in Clinical Nutrition, April/June, 2014;29(2):132-138). Your muscles, liver and fat cells are the only places where you can store significant amounts of sugar. Moving about after eating empties your muscles and liver of sugar, making room for more sugar to be stored there. See Skipping Breakfast May Harm Immune Response
Time-Restricted Eating May Not Be For Everyone
Time-restricted eating can be useful for people who want to lose weight, maintain their existing healthful weight, or keep from depositing excess fat in their liver. However, some conditions may be worsened or complicated by fasting. Discuss your plans with your doctor, particularly if you are diabetic, have low blood pressure, take medications, or are underweight. You will also probably be advised not to use intermittent fasting if you are pregnant, trying to become pregnant or breast-feeding an infant, if you are under age 14, or if you have a history of eating disorders.
My Recommendations
Time-restricted eating is healthful as long as you move around after you eat. The best time to eat is before or after you exercise because exercise helps to empty your liver and muscles of excess sugar, which can help to prevent a high rise in blood sugar after eating. I do not eat after 6PM and recommend that most people should do the same. See Move Around Before and After You Eat
