Intermittent Fasting: Surprising Update
The entire idea of IF is to allow the insulin levels to go down far enough and for long enough that we burn off our fat.
The Back Story on Intermittent Fasting
Intermittent fasting (IF) as a weight loss approach has been around in various forms for ages, but was highly popularised in 2012 by BBC broadcast journalist Dr. Michael Mosley’s TV documentary Eat Fast, Live Longer and book The Fast Diet, followed by journalist Kate Harrison’s book The 5:2 Diet based on her own experience, and subsequently by Dr. Jason Fung’s 2016 bestseller The Obesity Code, and Life Without Diabetes by Professor Roy Taylor, IF generated a steady popular buzz as anecdotes of its effectiveness proliferated.
The Obesity Code seemed the most evidence-based summary resource. Fung successfully combines plenty of research, his clinical experience, and sensible nutrition advice, and also addresses the socioeconomic forces conspiring to make us fat. He is very clear that we should eat more vegetables, fibre, healthy protein, and fats, and avoid sugar, refined grains, processed foods, and for goodness sake stop snacking.
Intermittent Fasting Can Help With Weight Loss
IF makes intuitive sense. The food we eat is broken down by enzymes in our gut and eventually ends up as molecules in our bloodstream. Carbohydrates, particularly sugars and refined grains (think white flours, pasta and rice)), are quickly broken down into sugar, which our cells use for energy. If your cells don’t use it all, we store it in our fat cells as FAT. But sugar can only enter our cells with insulin, a hormone made in the pancreas. Insulin brings sugar into fat cells and keep it there.
IF makes intuitive sense. The food we eat is broken down by enzymes in our gut and eventually ends up as molecules in our bloodstream. Carbohydrates, particularly sugars and refined grains (think white flours and rice), are quickly broken down into sugar, which our cells use for energy. If our cells don’t use it all, we store it in our fat cells as, well, fat. But sugar can only enter our cells as insulin, a hormone made in the pancreas. Insulin brings sugar into the fate cells and keeps it there.
Between meals as long as we don’t snack, our insulin levels will go down and our fat cells can then release their stored sugar, to be used as energy. We lose weight if we let our insulin levels go down. The entire idea of IF is to allow the insulin levels to go down far enough and for long enough that we burn off our fat.
Intermittent Fasting Can Be Hard…. But Maybe it Doesn’t Have To Be
New research suggesting that not all IF approaches are the same and some are actually very reasonable, effective and sustainable, especially when combined with a nutritious plant-based diet. We have evolved to be in sync with the day/night cycle, i.e, a circadian rhythm. Our metabolism has adapted to daytime food and nighttime sleep. Nighttime eating is well associated with a higher risk of obesity, as well as diabetes.
Based on this, researchers from the University of Alabama conducted a study with a small group of obese men with pre-diabetes. They compared a form of intermittent fasting called ‘early time-restricted feeding” where all meals were fit in into an early morning eight hour period of the day (7am to 3pm) or spread over 12 hours (7am to 7pm). Both groups maintained their weight (did not gain or lose) but after five weeks, the eight hours group had dramatically lower insulin levels and significantly improved insulin sensitivity, as well as significantly lower blood pressure. The best part? The eight hours group also had significantly decreased appetite. They weren’t starving.
Just changing the timing of meals, by eating earlier in the day and extending the overnight fast, significantly benefited metabolism even in people who didn’t lose a single pound.
Why Might Changing Timings Help?
But why does simply changing the timing of our meals to allow for fasting make a difference in our body? An in-depth review of the science of IF recently published a New England Journal of Medicine shed some light. Flipping the switch from a fed to fasting state does more than help us burn calories and lose weight. The researchers combed through dozens of animal and human studies to explain how simple fasting improves metabolism, lower blood sugar, lessens inflammation, which improves a range of health issues from arthritic pain to asthma; and even helps clear out toxins and damaged cells which lowers risk for cancer and enhances brain function. The article is deep and worth a read.
So, Is Intermittent Fasting As Good As It Sounds?
Metabolic expert Dr Deborah Wexler, Director of the Massachusetts General Hospital Diabetes Center and associate professor at Harvard Medical School said “There is evidence to suggest that the circadian rhythm fasting approach, where meals are restricted to an eight to 10 hour period of the daytime, is effective” though generally she recommends that people “use an eating approach that works for then and is sustainable to them.”
There is some good scientific evidence suggesting that circadian rhythm fasting, when combined with a healthy diet and lifestyle, can be a particularly effective approach to weight loss, especially to people as risk of diabetes. However, people with advanced diabetes or who are on medications for diabetes, people with a history of eating disorders like anorexia and bulimia, and pregnant or breastfeeding women should not attempt intermittent fasting unless under the close supervision of a physician who can monitor them.
4 Ways To Use This Information For Better Health
Avoid sugars and refined grains. Instead eat fruits, vegetables, beans, lentils, whole rains, lean proteins, and healthy fats (a sensible, plant-based, Mediterranean-style diet).
Let your body burn fat between meals. Don’t snack. Be active throughout your day. Build muscle tone.
Consider a simple form of intermittent fasting. Limit the hours of the day when you eat, and for best effect, make it earlier in the day (between 7am to 3pm, or even 10am to 6pm, but definitely not in the evening before bed).
Avoid snacking or eating at night time.
Sources
Effects of intermittent fasting on health, aging and disease. de Cabo R, Mattonsom MP. New England Journal of Medicine, December 2019.
Effect of Alternate-Day Fasting on Weight Loss, Weight Maintenance, and Cardioprotection Among Metabolically Healthy Obese Adults: A Randomized Clinical Trial JAMA Internal Medicine, May 2017
Alternate-day fasting in nonobese subjects: effects on body weight, body composition, and energy metabolism American Journal of Clinical Nutrition, January 2005.
The Obesity Code, By Jason Fung, MD (Greystone Books, 2016)
Intermittent fasting interventions for treatment of overweight and obesity in adults: a systematic review and meta-analysis. JBI Database of Systematic Reviews and Implementation Reports: February 2018
Metabolic Effects of Intermittent Fasting. Annual Review of Nutrition, August 2017.
Early Time-Restricted Feeding Improves Insulin Sensitivity, Blood Pressure, and Oxidative Stress Even without Weight Loss in Men with Prediabetes. Cell Metabolism, May 2018.