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Immortal Musings

The Longevity Diet

by Ralph Kenney

June 30, 2015

A new Article in the July issue of the research journal, Cell Metabolism has human longevity researchers excited.

The Thought Process Behind the Study:

Researchers at the Longevity Institute at The University of Southern California observed that alternating nutrient rich diet with fasting extended the life spans of some microorganism.

Prior research has established that fasting in humans promotes metabolic and cellular changes that reduce oxidative damage and inflammation, optimize energy metabolism and enhance cellular protection. Furthermore intermittent fasting has beneficial effects on insulin, glucose, C-reactive protein and blood pressure.

Recognizing that fasting is difficult for most people, they decided to investigate if a diet that simulates periodic fasting might have the same effect on humans. They call this dietary method the Fast Mimicking Diet (FMD).

Impressive Results for FMD in Mice:


They started with testing such a diet on mice and the results were impressive on many fronts. According to the research, mice on the FMD;

  • increased the number of progenitor and stem cells and regeneration of organs,
  • lived longer
  • lowered body fat
  • had reduced rates of cancer
  • rejuvenated their immune system
  • retarded bone mineral density loss (osteoporosis)
  • improved brain function (in older mice)
  • lowered insulin levels and lowered blood glucose levels.

The Human Study:

The researchers then performed a similar randomized clinical trial with people. For the human study, the subjects in the test group were given the FM diet 5 days per month. The rest of the time they were instructed to eat normally. They were asked not to make any changes in their exercise during the study, which lasted for 3 months. For comparison, there was an equal size control group who made no changes in either diet or exercise.

The Diet


For the 5 days per month that the human subjects were on the FMD their food was provided to them in a “diet box.” The study had an unusually high rate of compliance suggesting that this diet was relatively easy for people to follow. My completely unscientific guess is that subjects told themselves something like, “hey it’s only 5 days” so it was easier to stick with it verses an ongoing diet of indeterminate length.

The diet was designed by researchers to include micro- and macro-nutrients that reduced insulin and glucose, increased ketones, maximized overall nourishment and minimized any adverse effects. During the 5 day FMD period each month, calorie levels were reduced between 35% - 54%. The diet was structured to be 9%-10% proteins, 34%-47% carbs, 44%-56% fats.

The diet itself was vegetarian and while we don’t know the exact details we do know it was comprised of; soups, energy bars, energy drinks, chip snacks, chamomile tea and a supplement tablet. On day one of the 5-day FMD the subjects consumed 1,090 calories and on days 2-5 they consumed 725 calories daily.

Equally Impressive Results for the Human Study

After the 3 month study the researchers at USC report the following results;

  • an average of 3% weight loss with no loss of muscle mass (i.e. the weight lost was fat)
  • reduced risk of cardiovascular disease and reduced inflammation factors, of the test subjects who started the trial with moderate to high risk of heart disease, 87% tested as normal or low risk by the end of the study.
  • upward trending levels of regenerative stem cells and progenitor cells.

Overall the researchers summarized their findings as follows; “Although the clinical results will require confirmation by a larger randomized trial, the effects of FMD cycles on biomarkers/risk factors for aging, cancer, diabetes, and CVD, coupled with the very high compliance to the diet and its safety, indicate that this periodic dietary strategy has high potential to be effective in promoting human healthspan.”

They also cautioned that, for now, they only recommend the diet be used under medical supervision.

Why Does This Work?


Of course the researchers will spend a lot of time understanding in detail why this diet strategy has the benefits they observed. They have applied to the FDA to be able to prescribe this diet to patients for specific health conditions and this application is likely to result in considerable more research.

So, please take the following speculation with a big grain of salt. I tend to take a functional design perspective on the human body. The human body is clearly designed to survive under a wide range of conditions and has functional redundancy, self-adaptive feedback systems and self-repair capabilities.

This is why the human species has spread to every part of the globe and people are found adapted to the most extreme conditions on the planet. It is also why we can do some very unnatural things to our bodies like smoking or subsisting on primarily fast food and still thrive. Your body is designed to adapt and self-repair.

I think this diet works because it triggers some of these adaptive and self-repairing mechanisms by simulating a sudden onset of a short-term food shortage. Such events would have been fairly common for primitive people and our bodies are probably well designed to cope with these conditions. We are also probably well designed to recover quickly from these events, hence the uptick in regenerative processes and cells.

Why Doesn’t it Trigger the Infamous Diet Yo-Yo Effect?

One of the most problematic aspects of dieting is the yo-yo effect. We severely restrict diet for some time as part of a new diet regimen. Our body responds to the caloric restriction by slowing the metabolism. Then we stop the diet, for whatever reason. Our metabolism is still slower but our caloric intake returns to pre-diet levels. The result, we put the fat back on and then some.

So, at first blush this dietary strategy seems likely to trigger exactly that yo-yo response. But the study results indicate otherwise. Why not?

My guess is that it is the short-term nature of the pseudo-fast. Our body’s adaptations to reduced caloric intake are staged in order of increasing severity. Slowing the metabolism is a pretty severe response. The slower the metabolism the slower a whole bunch of necessary daily functions. From a survival perspective that’s bad. Under adverse conditions, your body needs to step up activity not reduce it. So, the first and simplest response is burning energy reserves stored as fat. After that, other coping mechanisms kick in. Only after prolonged famine conditions, does your body resort to slowing your metabolism.

Essentially, in response to a prolonged diet your body concludes, “OK, things are not getting better anytime soon, let’s just try to slow down and ride this thing out.” But in the case of the FMD, the restricted caloric intake is only five days. This is enough time to trigger several early stage coping mechanisms but not long enough to cause a slowed metabolic response. 

So When Do We Start?

New diets fads are constantly popping up. I have no doubt that this research will, at some point, spawn a new crop of best selling diet books. But, as I noted earlier, the researchers who conducted the study are currently only recommending this diet strategy under medical supervision. That’s probably an excess of caution. This diet is not a completely new idea and it is not that radical in nature.

But, we don’t know the exact details of the diet, especially the micro-nutrients involved and the devil may be in the details. So, my advice is wait for now until we know more. Let the researchers conduct their next round of research and hopefully reveal more details about the diet itself.

But, that said, I don’t see any harm in trying a 3-5 day period each month in which you moderately reduce calories, go vegetarian and in general try to eat better. It is likely to help reduce weight and flush toxins from your system. I believe there is a high probability of positive longevity effects.

As always, keep you own specific health condition in mind and be smart about it. If you have any specific concerns be sure to consult your doctor before starting this or any new diet regimen.

You can download the entire report here:


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