Obesity and the associated health concerns of cardiovascular disease, type II diabetes and metabolic disease are increasing in the developed world in spite of all of the information available on leading a healthy lifestyle. We know that we should stay away from excessive amounts of high-fat and high-sugar (mostly processed) foods and keep physically active. However, the reality of making wholesale changes in behaviour shows that most people find it difficult to lose weight. Researchers at the Salk Institute suggest that more innovative strategies, such as fasting, be considered.


Their recent and well-designed study looked at the effect of introducing a daily fasting period on various health measures while on a high fat, high sugar diet. Unfortunately, the study was conducted using mice (necessary in order to control the numerous metabolic factors in play) and the results may not be as effective in humans. However, the results are intriguing and worth noting.

They designed the study to mimic typical, non-dieting, human eating behavior ie the mice could eat as much as they wanted. Some mice were fed a normal diet; others fed a high fat/high sugar diet. Other groups of mice were restricted to feeding only during the specified periods, which ranged from 9 to 15 hours. Outside of these periods, they fasted.

What did they find?

Well, not surprisingly, mice fed a high fat/high sugar diet gained weight. But the mice that fasted for 9 – 15 hrs/day did not gain as much weight and those that had longer fasting times gained the least weight. Additionally, the mice on the fasting regimes had less fat mass, reduced total triglycerides levels in the liver, improved blood glucose balance, and reduced insulin resistance. Another surprising result was increased fitness via treadmill endurance experienced by the fasting mice. The researchers hypothesized that this might be due to enhanced capability of the metabolic pathways as a result of fasting.

The researchers also looked at the effect of relaxing the fasting schedule by allowing 2 days respite each week – 5 days on, 2 days off. The results were much the same.

What it all means

While this is very good news for overweight mice, what does it mean for us? If the results are similar in humans, this could be a game changer in how we combat obesity levels and associated health issues. The behavioral changes needed to adhere to the traditional strategy of calorie restriction and change in type of diet (whether low fat/low sugar/high carbohydrate) are too hard for most people to sustain in the long term. Daily fasting for at least 12 hours/day, while still a considerable behavioral or lifestyle change, is not as onerous and may well be as easy as implementing a ‘no snacking’ rule after dinner. For those looking for a new strategy now, it might be worth a try. I’m hoping that human trials start soon.


A Chaiz, A Zarrinpar, P. Miu, and S. Panda, ‘Time-Restricted Feeding Is a Preventative and Therapeutic Intervention against Diverse Nutritional Challenges’, Cell Metabolism, 20, 991-1005, 2014.

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    About the Author Sharon Walt

    Dr Sharon is a certified Functional Medicine Health Coach who helps men and women with autoimmune disorders, such as Hashimoto's Thyroiditis, regain their health and start living life to the utmost again.