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Intermittent Fasting for Weight Loss

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Circadian Rhythm, Intermittent Fasting and Weight Loss

— By Andrea M. Pampaloni, Ph.D.

Circadian rhythm is one of the most influential factors in how we function over the course of a day. In theory, this innate system maximizes energy levels in the morning upon awakening and helps to manage the metabolism throughout the day. However, life gets in the way and people can’t always listen to what their bodies tell them.

In ideal circumstances, people rise with the sun and eat a meal that would provide energy throughout the day. As the day progresses, cortisol levels decrease and melatonin increases so that as it becomes darker the body slows down to ready itself for sleep. In the real world, however, other factors such as work, children, geographic location and weather have a strong influence on what time an individual’s day begins and ends.

Because of these deviations from the natural circadian rhythm, eating cycles also are affected. Breakfast is forsaken in the rush to get to the bus or the office, and late nights at work or soccer practice could mean dinner isn’t ready until late in the evening. Instead, afternoon snacks and pre-dinner nibbles become the norm to ward off hunger until a meal can be put together. The problem with our extended, jam-packed schedules, especially when it involves shift work or other major disruptions, is that irregular mealtimes trigger a rise in insulin levels. Not everybody is able to counter this effect, which can lead to obesity, type 2 diabetes and heart disease.

Benefits of Intermittent Fasting

One way to address these fluctuations is through time-restricted feeding, also called intermittent fasting. This involves eating only during a certain period of time each day, usually within a window of six to 10 hours. This can be effective for weight loss because cells use the sugars produced by carbohydrates for energy before they become stored as fat and keep insulin levels low.

Research finds that it is not only limiting consumption to a defined period during the day that helps with weight loss, it also depends what time of day people eat. There is evidence to suggest that when food is consumed earlier in the day — prior to 4:00 p.m. — insulin levels and oxidative stress are reduced and β cell responsiveness and insulin sensitivity improves.1 Additionally, participants found that time-restricted eating was tolerable and helped reduce appetites so they didn’t feel hungry in the evening, potentially contributing to continued weight loss and health benefits.

Very Low Calorie Diets & Intermittent Energy Restriction

A Very Low Calorie Diet (VLCD) is a different type of intermittent energy restriction that achieves similar results. Meal replacements are nutritionally balanced to provide needed energy while helping to maintain balanced insulin levels. Further, studies demonstrate that combining intermittent fasting with a VLCD can improve risk indicators for coronary heart disease in women2, and increase exercise efficiency and reduce resting metabolic rate in other participants.3

This approach could also be an alternative for those whose schedules accommodate more frequent mealtimes, especially when combined with a VLCD program. In fact, some participants found fasting easier than trying to consume all their meals in a short period of time, so researchers suggest that an eight-hour window might be a more feasible option.


  1. Early Time-restricted Feeding Improves Insulin Sensitivity, Blood Pressure and Oxidative Stress Even without Weight Loss in Men with Prediabetes
  2. Intermittent Fasting Combined with Calorie Restriction is Effective for Weight Loss and Cardio-protection in Obese Women
  3. Compensatory Mechanisms Activated with Intermittent Energy Restriction: A Randomized Control Trial

About the Author: Dr. Andrea Pampaloni has over 20 years of communication experience across corporate, academic, nonprofit and government sectors. She provides research and writing services on a range of business issues and industry-specific topics to prepare white papers, articles, proposals, presentations, technical content, and speaking points, as well as marketing-communications content such as blogs, website content, newsletters, news releases and award submissions. Dr. Pampaloni’s research findings have been presented at national and international conferences and published in peer-reviewed journals, and she is a ghostwriter for three books, a Forbes article, and several corporate blogs.

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