Monthly 5-Day 'Fast' Supposedly Helps Healthy Humans to Keep Aging, Cancer, Diabetes & Heart Disease in Check

Even on the five fasting days per month your plate doesn't have to be completely empty. Real foods, however, weren't served in this trial.
An international consortium of scientists has recently published an intriguing study about the effects of a "fasting-mimicking diet" on markers/risk factors for aging, diabetes, cancer, and cardiovascular disease (Wei 2017). The study builds on the ever-increasing evidence that calorie restriction or changes in dietary composition can enhance healthy aging.

Now, as effective and healthy as it may be, fasting is not exactly what the average pre-diabetic (of whom the study at hand shows that he would benefit most) wants to do and/or what he or she can adhere to in the long run.
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To test whether it may not even be necessary to fast for weeks and months, Min Wei et al. conducted a randomized clinical trial with 100 generally healthy participants. With a cross-over after 50% of the study period of three months, the study ensured that all subjects were fed the fasting-mimicking diet (FMD) group for 3 months. Aside from being low in calories and protein -
  • day 1: ~4600 kJ = 1100kcal | 11% protein, 46% fat, and 43% carbohydrate 
  • day 2-5: ~3000 kJ = 717kcal | 9% protein, 44% fat, and 47% carbohydrate
- the diet that was consumed for 5 consecutive days per months for three months (with a lower kcal-deficit on day 1 vs. 2-5 that's supposed to make it easier to get into the fast), each, was plant-based diet, and designed to attain fasting-like effects on the serum levels of IGF-1, IGFBP-1, glucose, and ketone bodies.
Figure 1: Overview of the study design (left) and post hoc comparisons for changes in risk factors for age-related diseases and conditions by baseline subgroups (right | Wei 2017).
To compensate for the lack of macro and micronutrients the scientists used ready-made food products from USC and L-Nutra ( vegetable-based soups, energy bars, energy drinks, chip snacks, tea, and a supplement providing high levels (25% of the RDA per serving for most ingredients) of minerals, vitamins, and essential fatty acids were on the subjects' daily menu.
Figure 2: Overview of changes in several markers of metabolic and overall health (Wei 2017).
As you can see in the table on the right-hand side of Figure 1 and the series of graphs in Figure 2, fasting for only 5 out 30 days of a months and a total of 15 days in 3 months yielded quite impressive effects in all (Figure 2) and even greater effects in those subjects with lower metabolic health (see Figure 1, right) - a statistical significance between the improvements in those with the worst and best risk factors in Figure 2 was yet observed only for glucose and IGF-1.
The parameters improved, but you may still not live longer or stay healthier! It's not the lack of improvements in plasma lipids an it's neither the relatively small effect size of many changes. It is the mere fact that the glucose, insulin, IGF1 and triglyceride levels of the average Westerner will still skyrocket acutely on the 25 days of the months on which they don't fast. And that's really bad news, because many of the unassessed markers like the postprandial glucose and lipid levels are highly significant predictors of heart disease (Lefebvre 1998; Hanefeld 1999; O’Keefe 2007) or cancer (Michaud 2002; Prescott 2014; Larsson 2016) - to reduce the level of fasted / non-postprandi-ally measured markers of disease risk is thus clearly not enough to predict the true reduction of disease risk.
Bottom line: Overall, it is thus prudent to say that the three FMD cycles every subject underwent triggered significant reductions in body weight, trunk, and total body fat; lowered blood pressure and decreased insulin-like growth factor 1 (IGF-1) without serious side effects.

What looks like an easy way out does yet also have it shortcomings: (a) the subjects' blood lipids did not improve (neither total, nor LDL, or HDL cholesterol and their ratios); (b) the treatment may have been free of health-relevant side-effects, side-effects that will have many people fall off the wagon, however, existed, nevertheless (e.g. fatigue, weakness or headache see additional figure); (c) with no effect on peak values of glucose, insulin, IGF-1 etc. on the non-fasting days, it's far from being obvious that the treatment will have any of the hoped for long-term effect.

Especially (c) is something you should remember: before the scientists produce the long-term evidence that confirms that 5 days every month are enough to let you live longer, reduce your cancer, CVD and diabetes risk, I still recommend to change your lifestyle on 365 days of the year - that's the tried and proven method to live long(er) and healthy(-ier) | Comment!
  • Hanefeld, M., et al. "Postprandial plasma glucose is an independent risk factor for increased carotid intima-media thickness in non-diabetic individuals." Atherosclerosis 144.1 (1999): 229-235.
  • Larsson, Susanna C., Edward L. Giovannucci, and Alicja Wolk. "Prospective Study of Glycemic Load, Glycemic Index, and Carbohydrate Intake in Relation to Risk of Biliary Tract Cancer." The American journal of gastroenterology (2016).
  • Lefebvre, P. J., and A. J. Scheen. "The postprandial state and risk of cardiovascular disease." Diabetic Medicine 15.S4 (1998).
  • Michaud, Dominique S., et al. "Dietary sugar, glycemic load, and pancreatic cancer risk in a prospective study." Journal of the National Cancer Institute 94.17 (2002): 1293-1300.
  • O’Keefe, James H., and David SH Bell. "Postprandial hyperglycemia/hyperlipidemia (postprandial dysmetabolism) is a cardiovascular risk factor." The American journal of cardiology 100.5 (2007): 899-904.
  • Prescott, Jennifer, et al. "Dietary insulin index and insulin load in relation to endometrial cancer risk in the Nurses' Health Study." Cancer Epidemiology and Prevention Biomarkers (2014): cebp-0157.
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