Fast 5:2 Diet Evidence

By Joseph Constance, MAReviewed by Dr. Liji Thomas, MD

Fasting has been shown, in many research studies, to help us lose excess fat, improve our health, and lengthen our lives. Fasting from time to time was found to decrease the amount of body fat and improve the body’s sensitivity to insulin, in a study published by the British journal of nutrition. Research indicates that cutting one’s intake of calories by up to 40% can be a successful way to reduce weight and optimize health in general, and specifically heart health.

However, consuming few calories every day is sometimes difficult, especially for a prolonged period of time, so consumers are looking for more manageable dietary options. Among the variety of fasting regimens is the Fast 5:2 Diet, which calls for participants to eat normally five days of the week. The other two days requires restricting consumption to no more than about 600 calories per day.

The basic concept behind the Fast 5:2 Diet involves intermittent fasting, which is a trend that seems to be attracting followers. Proponents indicate that this approach can help achieve effective weight reduction, and that research backs this up.

Evidence

While some evidence has been generated showing the benefits of the Fast 5:2 Diet and intermittent fasting, much of the research has involved animal studies. But an apparently convincing human study was undertaken recently by investigators at the Genesis Breast Cancer Prevention Center at the University Hospital of South Manchester, Manchester, UK.

Approximately 100 overweight females followed a diet plan. As part of their regimen, the women consumed a Mediterranean-type diet for five days a week. On two days, the participants consumed few calories, eating lean protein and eliminating most other carbohydrates.

The researchers had theorized that an intermittent energy restriction approach could better improve insulin sensitivity and weight control than would energy restriction done on a daily basis. Once the study was completed, the participants found that they lost much more weight than those who attempted to limit calories for an entire week. Moreover, the diet had optimized their insulin resistance, which is a condition in which cells do not respond as they should to insulin.

The researchers determined that, at least on a short term basis, intermittent energy restriction does a better job than daily energy restriction in terms of optimized insulin sensitivity and the reduction of body fat. However, there is a need for long-term studies to examine the safety and effectiveness of intermittent fasting in humans.

Other research offers evidence that restricting the intake of calories along with intermittent fasting may improve nervous system health by affecting basic metabolic and cellular signaling pathways that influence neuronal life span. Apparently, both intermittent fasting and caloric restriction influence energy and oxygen radical metabolism, as well as modulate the stress response systems of cells in a manner that is protective for nerve cells. They essentially protect nerve cells from the adverse impact of genetic factors and the environment to which the cells would typically be exposed with aging.  

Additional research on intermittent fasting and caloric restriction, although not specifically involving the Fast 5:2 Diet, suggests that life span can be extended and resistance to age-related illnesses improved in non-humans. Moreover, the health of overweight people could be optimized. Heart and brain function also might be improved. Risk factors for stroke and other coronary illnesses, such as high blood pressure, could be minimized.  

Cardiovascular stress is modified in rodents on intermittent fasting or caloric reduction diets. And the brain and heart cells of rodents who undergo intermittent fasting better resisted ischemic injury from heart attacks and stroke. It appears that the benefits emanate from being better able to resist cellular stress and from reduced oxidative harm.

Apparently many people find it easier to take the Fast 5:2 day approach, even those who have difficulty with maintaining a daily diet routine. Once they adjust to low-carbohydrate, low-calorie eating for just two days in a week, they appear to consume less food overall.

Investigators themselves have tried out the diet routine. At the US-based National Institute on Aging, part of the National Institutes of Health, one researcher himself has followed the diet for some time. Though possessing a slender frame, he still restricts his eating and finds that it makes him feel better.

References  

1. http://www.npr.org/sections/thesalt/2013/07/29/205845319/two-day-diets-how-mini-fasts-can-help-maximize-weight-loss
2. https://www.ncbi.nlm.nih.gov/pubmed/23591120
3. http://scopeblog.stanford.edu/2016/07/07/intermittent-fasting-fad-or-science-based-diet/
4. http://www.sciencedirect.com/science/article/pii/S1568163706000523
5. http://www.pnas.org/content/100/10/6216.short
6. http://www.sciencedirect.com/science/article/pii/S0969996106003251
7. http://onlinelibrary.wiley.com/doi/10.1016/j.febslet.2007.02.006/full

Further Reading

• All Diet Content
• Low Calorie and Very Low Calorie Diets
• Diabetic Diet
• DASH Diet for High Blood Pressure
• High Protein Diet