Muscular Development|October 2021
Michael J. Rudolph

Like most good memes, old wives’ tales die hard, especially when they seem plausible and do no apparent harm. One of those sticky old wives’ tales I heard from my Mom throughout much of my childhood to persuade me and my two brothers to eat our breakfast was “breakfast gets the day’s work done.” I’m sure Mom had the best of intentions and was simply trying to get my two brothers and me to eat our healthy breakfast as we probably didn’t want to do anything except go outside to play. Now, I’m not saying my Mother was wrong, just inaccurate, especially considering a rash of recent scientific studies that show skipping breakfast, or even a few meals a day, every so often seems to distinctively promote enduring health benefits while also providing a terrific way to lose body fat. In fact, this dietary approach, known as intermittent fasting (IF), has become the latest diet craze. Yet, unlike many fads, IF is likely here to stay as science has uncovered several very important health benefits brought on by IF that are triggered by evolutionarily conserved, adaptive cellular responses that improve glucose regulation and bolster the body’s resistance to stress, while also suppressing inflammation throughout the body, altogether promoting health and wellness. IF has also been shown to promote substantial fat loss while uniquely maintaining lean body mass when combined with resistance training, unlike many hypocaloric diets that instead tend to promote the loss of body fat and muscle.

Different Fasting Approaches Provide Different Benefits

Three main IF protocols are currently employed. In “time-restricted feeding,” the individual only eats within a certain time window ranging from four to 12 hours throughout the day without trying to reduce caloric intake. Longer fasting protocols have also become quite popular, with one being alternate-day fasting where, as the name implies, the individual fasts completely every other day several times per week. Then there is the prolonged fasting method, which entails fasting for more than 48 hours.

Of the time-restricted protocols, the shortest restricted feeding window of four hours lowered inflammatory factors such as TNF-alpha and IL-6, indicating the capacity to reduce inflammation throughout the body.1,2 Inflammation is a normal process that can protect and heal the body following physical injury or infection. However, chronic inflammation is involved in a number of disease states. For instance, chronic inflammation in fat cells is closely related to the development of insulin resistance and type 2 diabetes. Interestingly, the four-hour feeding window also significantly increased glucose uptake into cells while also increasing other insulin action,3,4 suggesting the anti-inflammatory effect of four-hour time-restricted feeding contributes to improved insulin function.

The other time-restricting protocols of seven to eight5,6 and 10 to 12 hours7,8 also lowered and increased blood glucose in several studies, but had no impact on inflammatory markers or insulin function, implying longer feeding times preclude the anti-inflammatory impact of IF. Interestingly, the seven to eight and 10 to 12-hour time-restricted protocols promoted consistent weight loss ranging from 1% to 5% loss of bodyweight over four weeks, while the shortest four-hour feeding routine did not provide any weight loss, which was somewhat surprising as shorter feeding windows should reduce total caloric intake, promoting more weight loss.9 The potential reason for this unanticipated outcome is test subjects in these four-hour studies did time-restricted feeding every other day, permitting normal or even hypercaloric intake on off-days that mitigate any possible weight loss. Moreover, time-restricted feeding studies done in mice showed the four-hour feeding window led to the most consistent weight loss relative to the other time-feeding windows.

Alternate-day fasting and prolonged fasting protocols effectively improved multiple indicators of cardiovascular health including lowered cholesterol, triglycerides, and blood pressure while also reducing blood glucose and insulin resistance, suggesting an antiinflammatory effect from both of these fasting routines as well.10-12 Each of these two fasting approaches also promoted extensive weight/ fat loss as demonstrated in a study where subjects doing alternate-day fasting for three weeks lost 2.5% of their initial weight and 4% fat mass.13 Two additional trials involved overweight women assigned to either a prolonged fasting protocol where test subjects fasted for 48 hours straight per week, or underwent a more classic 25% reduction in daily caloric intake. Each group lost the same amount of weight during the six-month period. However, those in the prolonged fasting group had a larger reduction in waist circumference, which typically correlates with greater fat loss, suggesting alternate-day fasting caused more fat loss.14,15

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