Numerous studies on obese rats have shown that IF is very effective. They have better control of their blood sugar, cholesterol, and blood pressure and lose weight… However, they’re rats. Almost all human studies have demonstrated that IF works, although it’s not much better than other diets. Fasting is also challenging for many individuals.
However, a growing body of evidence shows that the timing of the fast is crucial and that this might make IF a more practical, durable, and successful strategy for weight reduction and diabetes prevention.
What led to the discovery of intermittent fasting
Even though intermittent fasting (IF) as a weight loss method has been around for a while, it only really gained popularity in 2012 as a result of Dr. Michael Mosley’s Eat Fast, Live Longer TV documentary and book The Fast Diet, journalist Kate Harrison’s book The 5:2 Diet, which was based on her own experience, and Dr. Jason Fung’s 2016 best-seller The Obesity Code. The neighborhood was often inundated with inspiring tales of IF’s achievements.
Fung examines the social reasons contributing to obesity with extensive research, clinical expertise, and sound nutritional recommendations in The Obesity Code. Fruits, vegetables, fiber, lean protein, and healthy fats are what he stresses most, while sugar, refined carbohydrates, processed meals, and snacking are what he stresses least.
Losing weight with the use of intermittent fasting
The logic behind IF is obvious. Enzymes in the digestive tract break down the food we consume into smaller molecules that are absorbed into the circulation. Our cells swiftly convert carbohydrates, especially sugars and refined grains (such as white flour and rice), into sugar for use as fuel. The excess is stored as fat in the body’s fat cells. Insulin, a hormone produced in the pancreas, is required for sugar to enter cells. Sugar is transported into fat cells by insulin and stored there.
In the time in between meals when food intake is minimal, insulin levels drop, allowing fat cells to release sugar for use as fuel. If we lower our insulin levels, we experience weight loss. Intermittent fasting (IF) aims to reduce insulin levels to a point where fat is burned.
The challenges of intermittent fasting… while maybe that isn’t necessary
Initial human trials comparing eating less every day versus fasting every other day found that both were roughly as effective for weight reduction, but many struggled with the fasting days. Therefore, choosing a Mediterranean-style plant-based diet with low calories makes perfect sense. But studies show that not all IF plans are the same and that specific IF diets are successful and durable, particularly when paired with a healthy plant-based diet.
We have developed a circadian rhythm that allows us to keep time with the day and night. Our bodies have become used to eating and sleeping throughout the day and night. An increased risk of obesity and diabetes is linked to night eating.
Researchers at the University of Alabama used this information to perform a study among a select sample of prediabetic overweight males. They compared eating all of one’s meals inside a narrow eight-hour window (from 7 a.m. to 3 p.m.), as in “early time-restricted feeding,” to eating normally during a 12-hour window (from 7 a.m. to 7 p.m.). Both groups kept the same weight (neither gain nor lose), but those who slept eight hours a night substantially improved their insulin sensitivity, blood pressure, and insulin levels after five weeks. Intriguing, right? The eight-hour sleepers also ate far less than the other groups. No one there was famished.
Even among people who didn’t lose weight, just shifting their meal times by eating earlier in the day and lengthening the overnight fast had a major impact on their metabolism.
Why would adjusting the time be useful?
But why does it make a difference in our bodies if we only shift our meal schedule to accommodate fasting? A new article in the New England Journal of Medicine comprehensively summarizes the research on IF. Instigating several critically critical cellular processes, fasting has evolved to be an integral part of human physiology. Changing our metabolic state from fed to fasting has benefits beyond weight loss. Researchers reviewed dozens of animal and human studies to explain how fasting, even brief periods of it, can have beneficial effects on metabolic rate, blood sugar levels, inflammation (which can cause everything from joint pain to asthma), and the elimination of toxins and damaged cells (which can reduce cancer risk and improve cognitive performance).
Is it true that fasting sometimes is as beneficial as it seems?
Dr. Deborah Wexler, the director of the Massachusetts General Hospital’s diabetes center and an assistant professor at Harvard Medical School, asserts that “there is evidence to suggest that the circadian rhythm fasting approach, where meals are restricted to an eight to ten hour period of the daytime, is effective.” However, she still advises individuals to “use an eating approach that works for them and is sustainable for them.”
Here’s the thing, then. When paired with a balanced diet and lifestyle, some robust scientific data show that fasting according to one’s circadian rhythm may be a highly successful weight reduction method, especially for those at risk for diabetes. Women who are pregnant or nursing, as well as those with a history of eating disorders such as anorexia or bulimia, should not try intermittent fasting unless they are under the direct supervision of a physician who can monitor them.
Here are four methods to improve your health, thanks to this data.
- Stay away from the white stuff. Eat a good, plant-based, Mediterranean-style diet full of fruits, vegetables, beans, lentils, whole grains, lean proteins, and healthy fats.
- Give your body time to burn fat in between meals. Avoid munching. Keep moving about all day long. Strengthen your muscles.
- Think about a basic fasting schedule. Avoid eating late at night if you want to lose weight, and try to eat between 7 a.m. and 3 p.m. or 10 a.m. and 6 p.m. at the earliest.
- Always try to refrain from eating late at night.
Based on work first published on the Uf52 by Dr. Nabeel Ahmad, M.P.H.
Sources
Intermittent fasting and health. R, MP. NEJM, December 2019.
A Randomized Clinical Trial on Metabolically Healthy Obese Adults examined the effects of alternate-day fasting on weight loss, maintenance, and cardioprotection. May 2017.
Alternate-day fasting in nonobese people: weight, composition, and energy metabolism. AJCN, January 2005.
Jason Fung, MD, The Obesity Code (Greystone Books, 2016).
Intermittent fasting for adult overweight and obesity: a comprehensive review and meta-analysis. Systematic Reviews and Implementation Reports, JBI Database, February 2018.
Intermittent Fasting’s Metabolism. Nutrition, August 2017.
Prediabetic Men With Early Time-Restricted Feeding Have Better Blood Pressure, Oxidative Stress, and Insulin Sensitivity Without Weight Loss. May 2018, CellMetabolism.
