Benefits of the 16:8 Diet – Backed by Science?

Also known as the 8-Hour Diet, the 16:8 Diet is a type of eating plan that entails not eating for 16 hours every day (including sleep), and only eating within an 8-hour window. Reportedly used by the Australian actor Hugh Jackman to get in shape for his Wolverine movies, this weight loss diet and health regime is based on the idea that allowing a 16-hour fast after an 8-hour eating period gives mitochondria, the power generators of your cells, a proper break from processing calories, resulting in significantly lower levels of free radicals in your body. Thanks to this break, the mitochondria should also function more efficiently.

But, does the 16:8 Diet actually work? Read on to learn what science is saying about the potential of this popular eating plan to deliver the results it promises.

Purported Benefits

There are several, slightly different versions of the 16:8 diet. One of the most famous ones is outlined in the book The 8-Hour Diet by author David Zinczenko and editor-in-chief of Men's Health Peter Moore. This 16:8 diet plan promises improved fat burning resulting in weight loss; reduced insulin resistance to slash your diabetes risk; enhanced brain function and a reduced risk of diseases affecting the brain such as Alzheimer's disease; reduced free radical load and cancer risk, and an increase in your levels of human growth hormone which helps keep you young and lean.

What Science is Saying

Characterized by a restricted eating period, the 16:8 Diet is a form of intermittent fasting (IF), and several studies have investigated the effects of intermittent fasting on health and weight loss. Here are some of the most interesting findings:

A review published in the journal Behavioral Sciences in early 2017 looked at recent studies comparing the weight loss effects of intermittent energy restriction and low-calorie diets, and concluded that intermittent energy restriction appeared to be as effective as low-calorie diets at reducing body weight in obese and overweight people. What's more, one of the studies included in this review reported a greater loss of body fat with low-carb intermittent energy restriction diets compared with low-calorie diets. [1]

A group of researchers led by James Johnson from Louisiana State University examined the effects of intermittent calorie restriction on asthma symptoms, pulmonary function, markers of oxidative stress and inflammation in overweight asthma patients. It is well known that obesity is a risk factor for asthma and that weight loss can improve symptoms in people with asthma. The results were promising: not only did the patients lose weight, they also showed improved symptoms within just two weeks. In addition, the levels of circulating ketones increased and the levels of leptin decreased on days when the participants' calorie intake was restricted, indicating that there was a shift in metabolism towards utilization of fatty acids. What's more, the improved clinical findings were associated with decreased levels of serum cholesterol and triglycerides, reductions in markers of oxidative stress, increased levels of the antioxidant uric acid, and reductions in markers of inflammation. [2]

A 16-hour nighttime fasting regimen has been shown to protect rodents on a high-fat diet from abnormal glucose metabolism, inflammation and weight gain, all of which are associated with the risk and prognosis of breast cancer. Intrigued by these findings, a group of researchers led by Dr. Ruth E. Patterson of UC San Diego investigated whether the duration of nightly fasting could predict cancer recurrence among women with early-stage breast cancer. What they found was that fasting fewer than 13 hours per night may increase the risk of breast cancer recurrence in women, suggesting that prolonging the duration of nightly fasting might be a good way to reduce the risk of breast cancer recurrence in women. [3]

An analysis of more than 2,000 women participating in the National Health and Nutrition Examination Survey found that longer nighttime fasting times were associated with reduced levels of the inflammatory marker CRP, but only in women who consumed less than 30% of their daily calories after 5 pm [4]. These findings echo the results of earlier animal studies which indicate that time-restricted feeding can reduce markers of inflammation in rodents.

Research suggests that exercise helps retain lean body mass in people on an intermittent fasting diet such as the 16:8 Diet. In one study involving 34 young adult men who performed resistance training, adherence to the 16:8 Diet reduced fat mass without destroying lean mass during the eight-week trial. The researchers also observed improved muscle endurance and a decrease in inflammatory markers among the men who took part in this study. [5]

BOOK YOU MAY LIKE
The 8-Hour Diet by David Zinczenko and Peter Moore is one of the best known books written on the weight loss and health benefits of the 16:8 Diet. David Zinczenko is the former General Manager of Rodale Inc.'s Healthy Living Group, and the author of the best-selling series, Eat This, Not That!. He has also appeared on Oprah, Good Morning America, Dr. Oz, Primetime Live, The Biggest Loser, The Rachael Ray Show, The Ellen DeGeneres Show, and numerous other programs. Zinczencko's co-author, Peter Moore, is the co-author of the New York Times bestseller The Lean Belly Prescription and former editor of Men's Health. Click here to check out The 8-Hour Diet on Amazon.

References:
1. M. Harvie and A. Howell (2017). Potential Benefits and Harms of Intermittent Energy Restriction and Intermittent Fasting Amongst Obese, Overweight and Normal Weight Subjects-A Narrative Review of Human and Animal Evidence. Behavioral Sciences (Basel), 19:7(1).
2. J. Johnson et al (2007). Alternate day calorie restriction improves clinical findings and reduces markers of oxidative stress and inflammation in overweight adults with moderate asthma. Free Radical Biology & Medicine, 1;42(5):665-74.
3. C. Marinac et al (2016). Prolonged Nightly Fasting and Breast Cancer Prognosis. JAMA Oncology, 2(8): 1049-1055.
4. C. Marinac et al (2015). Frequency and Circadian Timing of Eating May Influence Biomarkers of Inflammation and Insulin Resistance Associated with Breast Cancer Risk. PLoS One, 10(8).
5. T. Moro et al (2016). Effects of eight weeks of time-restricted feeding (16/8) on basal metabolism, maximal strength, body composition, inflammation, and cardiovascular risk factors in resistance-trained males. Journal of Translational Medicine, 14:290.