COOL NEW RESEARCH ON INTERMITTENT FASTING
In a brand new study from Annual Review of Nutrition (Metabolic Effects of Intermittent Fasting) researchers from the Department of Cancer, Department of Public Health, and Department of Endocrinology --- all from the University of California San Diego --- reviewed over 120 studies on the subject and came to some interesting conclusions.
- ALTERNATE-DAY FASTING: Food is consumed every other day (usually either two or three days a week). This type of fasting was "as effective as simple caloric restriction in reducing obesity-associated body weight and fasting insulin and glucose concentrations. Alternate-day fasting in rodent models of obesity has also been shown to reduce total plasma cholesterol and triglyceride concentrations, reduce liver steatosis and inflammatory gene expression, and have beneficial effects on cancer risk factors, such as cell proliferation." Some of the studies in this category also showed significant reductions in INFLAMMATORY BIOMARKERS as well. For the record, just realize that simple calorie restriction is not a great way to attempt to lose weight. A problem for people who did their fasting in this manner is that they never seemed to get over their hunger on fasting days.
- MODIFIED FASTING REGIMENS: Same thing as above, only instead of eating nothing on alternate days, modified fasters consume 20-25% of the normal amount of calories on those days. Some of the effects listed included "decreased visceral fat [BELLY FAT], leptin, and resistin, and increases in adiponectin.... appear to reduce adipocyte size, cell proliferation, and levels of insulin-like growth factor, statistically significant weight loss, decreases in fasting insulin, and one found reductions in fasting glucose, improvements in circulating LDL cholesterol or triglycerides, improvements in inflammatory markers, including C-reactive protein (CRP), tumor necrosis factor-α (TNF-α), adiponectin, leptin, and brain-derived neurotrophic factor (BDNF)." About 15% complained of irritability, lack of energy, hunger, etc, but overall, people on this diet felt better mentally and emotionally, had less anger and fatigue, and had more self confidence. They felt fuller as well. The authors did say that these benefits are not different than what studies have shown for people who simply restrict calories on a daily basis (something people are rarely able to stick with --- HERE).
- TIME-RESTRICTED FEEDING: This is what I do when I do it (the studies were on people who ate either one or two meals a day). The authors showed that this way of eating was associated with, "reductions in body weight, total cholesterol, triglycerides, glucose, insulin, interleukin 6 (IL-6), and TNF-α, as well as with improvements in insulin sensitivity.... reduces the risk of obesity and obesity-related conditions, such as nonalcoholic fatty liver disease, and chronic diseases, such as diabetes and cancer." Note that many of these studies are not on humans but on rats.
- MECHANISMS OF ACTION OF INTERMITTENT FASTING --- CIRCADIAN RHYTHMS: There are several areas of action that researchers looked at regarding intermittent fasting. These include circadian rhythms and sleep, microbiome, and energy intake -vs- energy expenditure. After talking about the way that most hormones such as INSULIN are on a 24 hour ebb-and-flow cycle, they stated that "As circadian rhythm synchronizers, it is hypothesized that fasting and time-restricted feeding regimens that actively impose a diurnal rhythm of food intake aligned with the 24-hour light–dark cycle lead to improved oscillations in circadian clock gene expression, the reprogramming of molecular mechanisms of energy metabolism, and improved body weight regulation. The potential effects of prolonged nightly fasting on energy intake, sleep, physical activity, and circadian activity rhythm may act in concert to reduce the risks of cardiometabolic disease and cancer. It is plausible that a chronically disturbed circadian profile may affect gastrointestinal function and impair metabolism and health." Working with this normal cycle instead of against it is critical (i.e. prolonging the fast by skipping breakfast) as opposed to disrupting the fast by eating late at night --- something that has repeatedly been shown to cause metabolic problems.
- MECHANISMS OF ACTION OF INTERMITTENT FASTING --- GUT MICROBIOME: I have shown you repeatedly that GUT HEALTH and MICROBIOME are critically important to overall health. These authors talked about research showing that dysbiosis-induced OBESITY could be "transferred" to thin mice via FMT. Not only did the authors suggest that fasting has the potential to help reverse DYSBIOSIS, but that, "extended fasting period (i.e., gut rest) could also lead to reduced gut permeability and to blunted systemic inflammation, which are typically elevated in obesity." Gut permeability refers to LEAKY GUT SYNDROME. And then we have the BRAIN-GUT PATHWAY. "Brain–gut pathways activated in the brain during fasting acts to promote energy balance by enhancing gut epithelial integrity." This is super cool because anywhere you have "THE LEAKIES" (Gut, brain, lungs, nerves, cord, etc), rest assured you will have SYSTEMIC HEALTH PROBLEMS. Thus, helping increase "epithelial integrity" goes a long way to solving lots of problems.
- MECHANISMS OF ACTION OF INTERMITTENT FASTING --- ENERGY IN / ENERGY OUT: While many studies showed that the benefits of fasting are no different than daily caloric restriction (aka "dieting"), the authors also said that "even a 1-day fast or 75% calorie restriction was shown to reduce caloric intake by approximately 30% during the subsequent 3 days." Furthermore, having always been an early riser, if I ever sleep in (which I never do anymore), I feel sluggish the entire rest of the day. Here is at least part of an explanation. "Animal studies indicate that the circadian clock regulates locomotion. Mice on a time-restricted, isocaloric feeding regimen [a single meal] have shown improved muscle coordination toward the end of the feeding period. Rodent studies demonstrate that time-restricted feeding regimens increase locomotion and improve circadian activity rhythms." Thus, movement is important, and movement is now known to be at least partially controlled by circadian rhythms.
It's clear that when you eat has a huge effect on circadian rhythms, which in turn has huge effects on both metabolism and energy levels, not to mention mental ability and outlook. Furthermore, numerous studies have shown that the number one way (by far) to increase lifespan is to eat about 60% of what you normally would eat. It seems that Intermittent Fasting is a potential method of helping people get closer to this goal (I have a post in the works on this topic). As always, whether you choose to fast intermittently or not, the KETOGENIC DIET or PALEO DIET are great diet choices and can both be done in an manner consistent with Intermittent Fasting. Also be aware that it is helpful to do an ELIMINATION DIET prior to anything you start so you can figure out what foods you might be reacting to immunologically.