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Reducing Metabolic Risk Factors By Temporary Fasting

To fast or not to fast.

According to a new published study, following a diet that mimics sporadic fasting over the course of 3 months reduced body weight and total body fat and improved metabolic markers in healthy adults.

Min Wei, PhD, from the University of Southern California in Los Angeles, and colleagues, writes, “These results indicate that the periodic (fasting-mimicking diet (FMD)) cycles are effective in improving the levels of an array of metabolic markers/risk factors associated with poor health and aging and with multiple age-related diseases.”

A benefit of their diet approach, they argue, is that it is easier and safer to adhere to than other types of stricter fasting. “Despite its potential for disease prevention and treatment, prolonged fasting is difficult to implement in human subjects and may exacerbate pre-existing nutritional deficiencies, making it not feasible and/or safe for children, the elderly, frail individuals, and even most of the healthy adults,” the authors write.

In an interview with Dr. Wei and co-author Valter Longo, PhD, they added that, “The results indicate that the diet will help prevent and treat diabetes, cardiovascular diseases, and cancer. It is clear that the FMD reduces diseases risk factors. However, more trials are needed.

Dr. Wei and colleagues randomly assigned 100 healthy U.S. adults to either follow a diet that mimicked sporadic, temporary fasting or to eat an unrestricted diet for 3 months. The FMD occurred for 5 consecutive days each month and used proprietary products from L-Nutra. Day 1 of the diet cycle involved consuming approximately 4,600 kJ (~1100 calories), including 11% protein, 46% fat, and 43% carbohydrates. During days 2 to 5, participants consumed 9% protein, 44% fat, and 47% carbohydrates to make up a total of 3,000 kJ (~717 calories) daily. The proprietary products included “vegetable-based soups, energy bars, energy drinks, chip snacks, tea, and a supplement providing high levels of minerals, vitamins, and essential fatty acids.” The diet aimed “to attain fasting-like effects on the serum levels of [insulin-like growth factor 1 (IGF-1), insulin-like growth factor–binding protein], glucose, and ketone bodies while providing both macro- and micronutrients to minimize the burden of fasting and adverse effects,” the authors explain.

At baseline, the two groups were similar in terms of the following metabolic markers or risk factors for age-related conditions: body weight, body mass index (BMI), total body fat, trunk fat, lean body mass, waist circumference, fasting glucose, IGF-1, systolic and diastolic blood pressure, triglycerides, and C-reactive protein. However, total cholesterol and low-density lipoprotein values were significantly lower in the initial intervention group at baseline.

After 3 months, participants in the intervention group lost an average of 2.6 kg of weight when assessed a week after completing the third fasting diet cycle vs no weight loss in the control group (0.1 kg). This weight loss primarily resulted from a reduction in body fat percentage and overall total body fat and trunk fat. In addition, the intervention group lost an average 4.1 cm in waist circumference, an average 21.7 ng/mL in IGF-1 concentrations, an average 4.5 mm Hg in systolic blood pressure, and an average 3.1 mm Hg in diastolic blood pressure.

However, no significant differences were seen for fasting glucose, triglycerides, total cholesterol, low- or high-density lipoprotein cholesterol, or C-reactive protein.

Then, after the first 3 months of the study, the control group participants switched in a crossover design to the dietary intervention for 3 months. Overall, 71 participants completed the diet intervention for a full 3 months, including 39 in the intervention during the first 3 months and 32 who were first in the control group before crossing over to the diet during the second 3 months. Between the two groups, the dropout rate from the intervention diet was 25%, primarily because of scheduling conflicts, personal issues, or dislike of the diet or lack of adherence to it.

Effects in the second intervention group (previously control) were comparable to those of the first intervention group except in two measures: A greater high-density lipoprotein reduction occurred in the first intervention group than in the second, and the first group showed a drop in absolute lean body mass that the second did not.

Combining results from the two groups revealed post intervention decreases in body weight, BMI, total body fat, trunk fat, absolute lean body mass, waist circumference, and all blood pressure and cholesterol values.

Assessment of the effect size based on BMI stratification showed that participants with a baseline BMI greater than 30 kg/m2 had a larger drop in BMI after the three cycles than those with a BMI below 25 kg/m2 or from 25 to 30 kg/m2. Similarly, those with a higher baseline blood pressure showed greater proportional reductions in blood pressure measures after the intervention.

The participants reported no serious adverse effects during the intervention.

Among 50 participants who returned for a voluntary follow-up 3 months after completing the last diet cycle, the changes in body weight, BMI, blood pressure, and IGF-1 remained, as did the drop in blood glucose seen only in at-risk participants. These findings may indicate lasting beneficial effects from the diet.

The authors also noted the possibility that the dropout rates indicated potential difficulty in adhering to the diet.

Practice Pearls:

  • Periodic (fasting-mimicking diet (FMD) cycles are effective in improving the levels of an array of metabolic markers/risk factors associated with poor health.
  • Benefits were seen for decreases in body weight, BMI, total body fat, trunk fat, absolute lean body mass, waist circumference, and all blood pressure and cholesterol values.
  • The findings may indicate lasting beneficial effects from the diet.

For More on Fasting: Dr. Mark Mattson intermittent fasting video series – an exclusive discussion with Diabetes in Control. In part one of this special interview, Dr. Mark Mattson and DIC publisher Steve Freed discuss Dr. Mattson’s research into brain aging and neurodegenerative disorders, and the positive effects of intermittent fasting in delaying aging and preventing .

Sci Transl Med. Published online February 15, 2017. Abstract , according to a study published today in Science Translational Medicine.