Weight loss and IF
In a few high-quality human trials, IF has been proven to reduce weight to a similar level as typical caloric restriction-based diets, but it has not been proved to be any more successful. One of the high-quality studies I mentioned earlier discovered that “alternate-day fasting did not provide greater adherence, weight reduction, weight maintenance, or cardioprotection vs. daily calorie restriction.” And the other (also one of the high-quality ones I highlighted) stated that “three (fasting) cycles lowered body weight, trunk, and total body fat…” as well as a slew of other characteristics that need to be investigated further in future clinical studies. Fasting one full day every other day, five consecutive days once a month, and two non-consecutive days per week were common IF regimens in those and other research. Unfortunately, these regimens were difficult for participants to stick to.
Many proponents of intermittent fasting believe that it promotes fat loss by modifying hormone levels; however, researchers say that these hormone changes aren’t significant enough to produce weight loss in this manner. “There are hormonal changes with intermittent fasting, but none are severe enough to be clinically significant,” Deena Adimoolam, M.D., assistant professor of endocrinology at Mount Sinai, tells SELF. “For example, several intermittent fasting methods mention an increase in growth hormone levels causing fat reduction. Growth hormone can cause an increase in lean body mass; however, considerable amounts of growth hormone are required to achieve this, which intermittent fasting does not provide.” Again, additional research on this area is required before drawing any firm conclusions.
Diabetes and IF
Suppose has also been studied for its effects on many physiological systems, including metabolic, cognitive, and cardiovascular benefits. For example, one solid study among persons with diabetes found that IF was as efficient (but not better than) a traditional weight loss diet at reducing hemoglobin A1c, which is a metric of average blood sugar over the previous few months.
The study of IF as a hemoglobin A1c management approach in patients with diabetes found that IF is an alternative that may work in place of other diet techniques used for blood sugar control. However, it is crucial to remember that IF does not replace drugs used to treat or manage diabetes. Using IF to treat a chronic condition like diabetes is a secondary prevention technique. You try to avoid the disease worsening or progression and should be done under the supervision of a physician.
IF and cardiovascular health
This is where we go into the research that my colleagues and I have been working on for years. First, some context: What first piqued my interest in investigating IF was a series of studies conducted by the University of Utah around 40 years ago, which revealed that death rates in Utah from most malignancies and heart diseases were significantly lower than those in the rest of the United States. This was attributed to Utah’s low smoking rate. A UCLA study published around the same time found that religiously devoted members of the Church of Jesus Christ of Latter-day Saints in California lived longer than other Californians, with a life expectancy of more than seven years longer. In 1998, I enrolled in an epidemiology course offered by one Utah researcher. There was no academic research on IF at the time, but fasting (a regular and prevalent practice in the Church of Jesus Christ of Latter-day Saints) stood out as a potential heart-protective activity that had not yet been formally explored.
The study’s findings in 2008 were remarkable. Even after controlling for various other characteristics and behaviors, those who reported habitually fasting had a much lower risk of being diagnosed with the coronary disease than those who did not fast. In addition, although it was not our primary hypothesis, fasters had a lower likelihood of diabetes. To see if the diabetes conclusion was correct, we did another study in 2012 that asked the identical fasting question but focused on whether it was connected with diabetes.
In my 2008 and 2012 investigations, the typical fasting participant had fasted around one day per month for 45 years (their age averaged 65 years). This showed that some of the results we see from IF were due to IF being used as a long-term lifestyle change rather than a short-term cure for, for instance, weight loss. It had taken decades for the cardiovascular and diabetes benefits to becoming clear. That wasn’t necessarily a terrible thing. Because heart disease, diabetes, dementia, and other chronic non-infectious diseases often develop over decades, having a little chronic protection via an IF lifestyle over that time could (and we anticipate it would) prevent those diseases from forming and silently worsening.