Fasting Pros and Cons
Is fasting a good way to lose weight?
In my previous article I explained a little bit about the more popular fasting programs for weight loss. There are 24-hour fasts where you eat nothing for a full day once or twice a week; Intermittent daily fasts where you restrict your eating to daily windows between 4 and 10 hours; And low calorie, regular calorie days where you eat normally one day and then just 500-700 calories on the “fasting” day.
Versions of these programs have gone mainstream over the last few years. The most important question I have is; do they work?
According to several studies, the answer is yes. However, they don’t appear to work any better than traditional reduced-calorie diets. In a review of 31 studies, researchers found that intermittent fasting “appears to produce similar effects” to regular calorie-restricted diets. It also does not appear to “improve weight loss efficiency” when compared to traditional calorie-restricted diets.
The conclusion of one major study stated that, “Intermittent fasting thus represents a valid--albeit apparently NOT SUPERIOR --option to continuous energy restriction for weight loss.”
If other diets have failed you, fasting may be the way you’re finally able to have a breakthrough. Just as some people were able to achieve success with lower fat, lower carb or higher protein diet plans, intermittent fasting may be the trigger that gives you long-term success.
Before you make a decision, lets clear a few misconceptions up. Supporters claim that fasting strengthens bones, improves circulation, protects your organs, decreases the signs and symptoms of aging or that it promotes healthy hair and nail growth. Unfortunately no. Fasting has never been shown to directly cause any of those things.
Some of the things attributed to fasting, are the byproducts of losing weight. For example, one program claims that fasting decreases fat accumulation. Well, yes. But any diet that causes you to lose weight, will lower how much fat you carry around. The same is true for cholesterol. People who lose weight on almost any diet, typically see an improvement in their cholesterol profile, not just the people who lose weight by fasting.
There is one big benefit of fasting. It helps people understand true physical hunger. In the modern world, we have constant access to food. We also tend to use food as a crutch for when we’re bored, or thirsty. When you start a fasting program, you learn that sometimes you eat to fill an emotional void, not because you need to eat. Or that drinking a glass of water is better than candy, because that craving you feel is thirst, not hunger.
Fasting may be an appropriate diet program if you’re unable to eat fewer calories regularly. You might find more success losing weight by being forced to simply not eat at all.
When should you NOT fast?
Fasting may accelerate any metabolic slowdown. If you stop eating for long periods, 24 hours or more, your body tends to burn muscle and hangs onto fat, because it thinks you’re starving. That means anyone who’s trying to build more muscle, might want to consider another program.
Going into a workout after fasting, is also not the best idea. Eating food gives you energy. You need energy to get through a workout. Eating a small meal, 60 to 90 minutes before exercise gives you the energy to push harder and get through a more intense workout.
Think about it. When you work on something for a few hours, eventually you'll hit a "wall." It's a point when you're mentally and physically exhausted. The common solution is to take a break and have something to eat. After your meal, your body has more energy to draw from, you feel refreshed and you're able to get more work done. It's the same principle when you eat before exercise.
Fasting after a workout is another bad idea. When you finish exercising, your body needs fuel to rebuild. Your body is in a "catabolic state." That means muscle glycogen is depleted and increased cortisol levels begin to break down muscle tissue. Eating properly can slow muscle breakdown and speed recovery.
WARNING!
Anyone on a regular exercise program should skip fasting on days they plan to workout. You should also consider another weight loss method if you have any chronic diseases; if you’re a pregnant or nursing woman; children under the age of 18; adults over 60; people dealing with diabetes and anyone who should closely monitor their blood sugar. If you’re in any of those groups, talk to your doctor or health care provider and follow their guidance.
Part 1 2
UPDATE 10/4/2020
Additional studies show that eating breakfast is critical for weight loss and muscle growth. You can read more here: Is Skipping Breakfast a Good Way to Lose Weight? - Intermittent Fasting, Breakfast and Weight Loss
UPDATE 4/20/2024
A study released in April of 2024 showed minimal differences in weight loss between groups that engaged in Time-Restricted Eating (Intermittent Fasting) and traditional calorie counting.
Any weight loss benefits of Time Restricted Eating were attributable to reduced caloric intake rather than the eating pattern itself.
Effect of Isocaloric, Time-Restricted Eating on Body Weight in Adults With Obesity: A Randomized Controlled Trial
Nisa M. Maruthur, MD, MHS, Scott J. Pilla, MD, MHS, Karen White, MS, RDN, Beiwen Wu, MSPH, RDN, May Thu Thu Maw, MBBS, MPH, Daisy Duan, MD, Ruth-Alma Turkson-Ocran, PhD, MPH, APRN, Di Zhao, PhD, Jeanne Charleston, RN, BSN, Courtney M. Peterson, PhD, Ryan J. Dougherty, PhD, Jennifer A. Schrack, PhD, Lawrence J. Appel, MD, Eliseo Guallar, MD, DrPH, and Jeanne M. Clark, MD, MPH
Annals of Internal Medicine, Published 19 April 2024
UPDATE 4/20/2024
A new review by researchers from the University of Southern Denmark and Wageningen University in the Netherlands looked at existing data on intermittent fasting and weight loss. The main finding is that while intermittent fasting involves skipping meals for extended periods, weight loss ultimately requires a reduction in overall calorie intake. Simply going for long stretches without eating does not guarantee fat loss if total calories are not controlled. As molecular biologist Philip Ruppert from the University of Southern Denmark explains, “intermittent fasting does not give you a free pass for eating unlimited quantities of food.” The essential principle remains that you must consume fewer calories than you burn to lose weight.
Reference Links:
Do intermittent diets provide physiological benefits over continuous diets for weight loss? A systematic review of clinical trials
Radhika V Seimon, Jessica A Roekenes, Jessica Zibellini, Benjamin Zhu, Alice A Gibson, Andrew P Hills, Rachel E Wood, Neil A King, Nuala M Byrne, Amanda Sainsbury
Molecular and Cellular Endocrinology, Published 2015 Dec 15:418 Pt 2:153-72. doi: 10.1016/j.mce.2015.09.014. Epub 2015 Sep 16.
Intermittent versus daily calorie restriction: which diet regimen is more effective for weight loss?
K A Varady
Obesity Reviews: An Official Journal of the International Association for the Study of Obesity, Published 2011 Jul;12(7):e593-601. doi: 10.1111/j.1467-789X.2011.00873.x. Epub 2011 Mar 17.
Call for a FREE Consultation (305) 296-3434
CAUTION: Check with your doctor before
beginning any diet or exercise program.
6/16/2018
Updated 10/4/2020
Updated 4/20/2024
Updated 1/17/2025
