Did you know that this month is the second national Fasting February? Launched by the company that created the LIFE Fasting Tracker app (in concert with National Day Calendar), this month is about promoting and teaching healthy ways of intermittent fasting, to keep not only weight in check but to boost and sustain overall health and vitality.
What is Fasting?
Fasting is a defined period of abstinence from consuming food and even water, although the latter is rather extreme. Humans can live longer without a morsel of food than we can without a drop of water (or water-containing foods/drinks). According to researchers of one paper exploring intermittent fasting’s impact on metabolic health, fasting “has been practiced since earliest antiquity by peoples around the globe.”
Types of fasting for which studies have been performed are intermittent (including alternate day fasting) and modified fasting. Intermittent fasting is only eating in an 8-hour window and not eating or drinking (except some water) for the remaining 16, including sleep time. Alternate day fasting is a fasting day with no food or drink (water is ok), followed by day of normal eating. Modified fasting allows for some consumption on fasting days but very little, perhaps about 20 to 25% of what you would normally have. This, type of fasting is also known as 5:2—five normal eating days and two intermittent—not consecutive—calorie-restricted days in a week.
Intermittent fasting has been shown in several studies to exert a health boost: significant reduction of blood sugar levels and reduced insulin resistance.
One 15-day study of eight healthy young men who performed an intermittent fast every second day for 20 hours found that they maintained their healthy body weight but experienced increases in insulin-mediated glucose uptake rates (better blood sugar response).
In another clinical investigation, non-obese men and women fasted every other day for 22 days. Their body weight, body composition, resting metabolic rate, respiratory quotient, body temperature, fasting blood glucose/insulin, and the hormone ghrelin (the hunger hormone) were all measured at the beginning of the study, at day 21 with a 12-hour fast, and the next, final day (36-hour fast) of alternate day fasting. Participants lost 0.5% of initial body weight and showed significant fat oxidation although this study did not find significant changes in glucose and ghrelin numbers.
Meanwhile, based on previous research suggesting that periodic fasting was associated with a lower prevalence of coronary artery disease, researchers looked at healthy volunteers who have not fasted in a randomized crossover trial featuring a one-day water-only fast. Interestingly, the research team found that the one-day fasting acutely increased human growth hormone, hemoglobin, red blood cell count, total cholesterol and the good cholesterol—high-density lipoprotein, and decreased triglycerides. They concluded that “fasting induced acute changes in biomarkers of metabolic, cardiovascular and general health” and that “repeated episodes of periodic short-term fasting should be evaluated as a preventive treatment with the potential to reduce metabolic disease risk.”
Modified fasting also has shown decent results in those who are overweight or obese, in trials ranging from 8 weeks to 6 months. According to the aforementioned review, six studies reported statistically significant weight loss, ranging from 3.2% to 8%. Two studies showed significant reduction in fasting insulin but not in fasting glucose. Three studies showed good improvements in blood fats (lipids). Two studies showed strong improvements in inflammatory markers such as C-reactive protein, tumor necrosis factor-alpha, and in appetite/satiety hormones adiponectin and leptin.
Exercise helps, you just can’t get around that. Along with the fasting of your choice, getting some exercise will accelerate weight/body composition goals and improve health parameters. For example, one 12-week, controlled weight loss trial of 64 obese individuals found that modified fasting combined with exercise produced significantly superior weight loss results (6.5%) compared to fasting alone (3.2%) or exercise alone (1.1%).
Another study assessed the impact of alternate-day calorie restriction (ADCR) or exercise –on cardiometabolic risk factors in 35 overweight or obese but healthy adults –the combination of ADCR and exercise proved to be beneficial, most effective at inducing beneficial changes in body weight and composition, glucose, insulin, insulin resistance and triglycerides.
Researchers in a newly published meta-analysis found that intermittent fasting (also known as TRF or time-restricted feeding) was suggested to be a factor in a significantly higher weight loss and lower fasting glucose values compared to controls with unrestricted time of food intake. In observational studies, noted the authors, TRF led to a significant reduction of body mass index, free fat mass, and systolic blood pressure.
Fasting and Inflammation
Intermittent fasting has been shown to be favorable in managing healthy inflammatory response. Unhealthy inflammation is characterized by continual over-production of biochemicals that cause inflammation in organs and systems. Unlike a fever (a healthy kind of inflammation), you don’t feel this type.
One study investigated how the intermittent fasting practice of Muslims during the holy month of Ramadan found that 50 healthy volunteers; eating is restricted for 12 hours a day for one month during the day. The researchers quantified pro-inflammatory markers, weight and body fat percentage one week prior to the month, during the month and after. They found that after the time of intermittent fasting, pro-inflammatory biochemicals, weight and body fat percentage were significantly lower. They concluded that intermittent fasting “attenuates inflammatory status of the body by suppressing pro-inflammatory cytokine expression and decreasing body fat and circulating levels of leukocytes.”
Another similar investigation of 40 healthy volunteers of normal weight came to the same conclusion, that prolonged intermittent fasting generates positive impact on the body’s inflammatory status.
Fasting & Your Microbiota
The several types of light fasting modalities can certainly improve overall health and fitness status after time. And it also appears through some initial clinical observations that intermittent fasting can promote healthy microbiota and microbiome structure and function in a variety of conditions.
For example, according to authors of one research paper, “Intermittent fasting has been hypothesized to promote metabolic health through the effects on gut microbiota.” And in a murine model, intermittent fasting was shown to reshape/replenish the gut microbiota composition. Additionally, this study showed that intermittent fasting increased acetate and lactate levels, which directly influences browning of adipose tissue, a desired activity in promoting weight loss and related health parameters.
Other findings strongly suggest that habitual intermittent fasting protects against development of diabetic retinopathy by restructuring the microbiota toward species producing a neuroprotective bile acid and subsequent retinal protection.
Intermittent fasting may take a little while to get used to. But the benefits are numerous and will seed the motivation to continue. Further, you will find that it is truly not difficult to follow, no matter which pattern you choose. One piece of advice is that if you feel a bit hungry, drink water. Do something productive, like a chore or a brisk walk around the neighborhood. After only a few weeks, your appetite will adapt. After six months to a year, your doctor should present you with great news: more favorable blood sugar, blood pressure and cholesterol profiles.
Intermittent fasting also tips the microbiota in a favorable balance. It stands to reason that taking probiotics daily can further bolster the strength of the microbiota structure.