Fasting is a powerful way to achieve optimal physical and mental health, used for generations by multiple cultures across the planet, yet I find so many patients, physicians, dietitians and other colleagues in health care either skeptical or fearful of its potential harm. I want to address a few of the top myths about fasting I come across in my practice. For some background on fasting, read this post and refer to my book as well.
Myth #1-Fasting Will Slow My Metabolism
Fasting and low calorie diets are not the same thing and have different impacts on our hormones and overall physiology. Fasting actually increases the release of adrenaline, which revs up metabolism and facilitates lipolysis (aka fat burning). This gave our ancestors energy so they could seek food during times of famine. This is different than eating a chronically low calorie diet which actually slows down metabolism as shown in this study, leading to rebound weight gain.
If fasting slowed down metabolism, then our primal ancestors who were subjected to long fasting periods during inclement weather and caloric scarcity, would be fatigued and fat, but instead they were energetic and lean, exactly what my patients become when they strategically incorporate intermittent fasting into their life.
By the way, eating more frequently to boost metabolism is a dangerous myth that leads to more fat storage and a slower metabolism in the long run. You may see lean and fit athletes eat this way, but they had a high metabolism already so frequent eating simply fuels their robust metabolic engines.
For most sedentary, overweight and especially insulin resistant individuals, eating more often rarely leads to significant and lasting positive body composition changes and instead contributes to more weight gain.
Key Point: Low calorie dieting slows down metabolism and fat burning, while fasting does the exact opposite. Don't equate fasting with low calorie diets.
Myth #2-Fasting Will Break Down Muscle
Once again, don't confuse strategic fasting with chronic low calorie or yo-yo dieting. Individuals who overexercise and undernourish themselves with nutrient deficient cleanses and extreme diets will eventually break down muscle, which will lead to myth #1 (a slower metabolism) and fat gain when they come off their temporary diet.
Our bodies are designed to preserve muscle in times of fasting which is why fasting actually triggers a potent release of growth hormone. Again, look at pictures of our primal ancestors. They possessed lean, muscular frames rather than rickety, muscle-deficient ones. Most of us have abundant glucose stores in our liver and muscle which we access first when we fast. When we run out of stored glucose, we can then access our even more prolific stores of body fat. Breaking down muscle for energy is the absolute last reservoir.
In today's fitness and body-building world, more and more professionals are adopting periods of intermittent fasting to achieve their 2 primary goals…burn excess fat and retain lean muscle. This strategy also helps our not so athletic types.
What really breaks down muscle in most patients I see in clinic? A lack of proper resistance training or over-resistance training in the absence of proper rest/recovery periods, a lack of sleep (deep sleep is a key way to promote growth hormone release),a sedentary lifestyle typical of modern life, protein-deficient diets (especially in my vegetarian patients-read this post for guidance) and chronic stress (stress is a catabolic state that breaks down muscle tissue).
I take care of some elite athletes and many of them get over 10 hours of sleep because they know that's the best way to get natural, legal doses of growth hormone into their bloodstream. Their rest days are truly rest days where they get deep tissue massages, sit in saunas (another good trigger for growth hormone you can read about in my sauna post here) and whirlpool baths, etc.
Contrast this with my patients who habitually sleep less than 8 hours, are under chronic stress, eat a protein deficient diet and lack dedicated “rest days” during the week. Even weekends involve late night social events and shuttling kids back and forth between sports practices and activities. These events may be enjoyable, but they don't count as rest. I know most of us can't lead the life of elite athletes, but we have plenty of opportunities to extend sleeping hours and get more rest.
Key Point: Intermittent fasting preserves and protects muscle mass rather than breaking it down.
Myth #3-Fasting Triggers Hunger and Overeating
Eating triggers hunger and overeating, not fasting. Especially eating modern day foods infested with sugar and artificial ingredients specifically and scientifically designed to be addictive. I'm writing this section at 11:44am and I finished dinner yesterday at 7p. This means I haven't eaten in over 16 hours (sorry Mom if you're reading this…don't worry, I'll be ok!) and I feel fine. Give me a handful of Doritos or a slice of toast and all of a sudden my hunger cycles will begin.
If you are eating today's standard diet, then your hunger is a victim to glucose and insulin levels that surge and crash throughout the day. You are not in control of your food. Your food is in control of you. In this case I actually do not recommend starting fasting right away.
Eat a clean diet first as recommended here in my blog and in my book. Once your glucose and insulin swings start to stabilize, then your body is prepared to try periods of intermittent fasting. If your diet is poor and then you try to fast, it may feel like torture and you may never try it again. That would be a tragic loss.
Telling someone to fast when they're eating a poor diet is like telling someone who has never exercised to start running marathons or doing boot camps…unfortunately a common practice I see here in Silicon Valley which leads to injuries and even severe complications like heart attacks.
Your hormones and metabolic machinery are not equipped to help you sail effortlessly through a fast if you're not eating the right foods in the first place. You need to get your diet “in shape” for fasting, rather than using fasting as a way to constantly detox from an unhealthy diet.
One of the benefits I enjoy most from intermittent fasting is a reduced reliance on food. Eating less frequently means I exert far less time and energy thinking about where to find my next meal or snack. This means spending more time with my family or writing blog posts that you can benefit from. It is incredibly liberating!
Key Point: Intermittent Fasting resets and reduces hunger. Eating unhealthy foods and eating more frequently increases hunger.
Myth #4-My Blood Glucose Might Drop Too Low
Your body is a glucose-storing and glucose-making machine. Glucose levels typically stabilize and over time we see tremendous improvements and even reversal of insulin resistant conditions like diabetes with strategic intermittent fasts.
Hypoglycemia (abnormally low blood glucose) is only a precaution in diabetics if they are taking insulin or oral pills that lower glucose. In these cases you need close supervision by a professional and you need to monitor your glucose levels closely if incorporating fasts.
You may want to start off with shorter interval fasts while keeping tabs on your glucose levels. Injectable insulin and/or other glucose-lowering medications can be tapered down by your physician when blood glucose levels show consistent improvement.
Key Point: Intermittent Fasting stabilizes blood glucose and can potentially reverse diabetes.
Myth #5- Fasting is too Hard
Fasting is completely natural and is encoded into our DNA. Modern life has made fasting seem impossible for many of the reasons I've discussed above. Don't make it seem harder than it actually is. If you finish dinner by 7p and skip breakfast the next day and have an earlier lunch at say 11a, you will have successfully completed a 16 hour fast.
Remember, you are not “slowing down your metabolism” by skipping breakfast. Ignore what you've heard about in studies showing improved weight loss in breakfast eaters. Most of these studies are terribly designed with confounding factors and many are financed by breakfast cereal companies. Eating breakfast 7 days a week is an unnatural habit created by big food corporations. If you eat a healthy breakfast and enjoy great health and a normal body composition, then no need to skip. If you are struggling with your weight and overall health and don't feel hungry in the morning, forcing food into your mouth in an effort to help with weight loss may not be a rational solution. Read this NPR article for more information.
When you do eat, eat nutrient dense foods with lots of vegetables, proteins and healthy fats. With the cold weather now, I drink all types of herbal teas during my fasting periods to stay hydrated. I'll add a pinch of cinnamon, fresh mint leaves and/or a small dollop of extra virgin coconut oil. This is acceptable during the fasting period.
If “fasting” turns you off, just call it “breakfast skipping.” Get to bed earlier so you produce more growth hormone through the night while leveraging sleeping time as fasting time. Going to bed later (after 10p) means more time to get the late night munchies and also less growth hormone production.
Make occasional periods of fasting a goal and pay attention to the impact it has on your energy, body composition, ability to focus, your blood glucose or whatever health goals you follow.