Intermittent fasting has been used medically since at least the 5th century BCE. Greek physician, Hippocrates, the “father of medicine” himself, recommended abstinence from food or drink to certain sick patients.
Ancient Greece is often crowned as the birthplace of fasting, but it was part of the religious lifestyle of different groups worldwide long before the 5th century.
This ancient practice supports healthy metabolism and immune function — essential elements of long-term health in our modern world. Yet today, intermittent fasting is under scrutiny.
So what’s true? Is intermittent fasting one of the most tried and true health practices of human existence? Or is it an outdated, unhelpful, even harmful practice that should stay in the past?
Let’s take a close look at 6 criminalizing claims about intermittent fasting and see what the science says.
Nope! Your body will not slip into starvation mode while you’re looking the other way.
The term “starvation mode” has drifted from its original meaning. What people generally refer to as “starvation mode” is simply a slowed metabolism (which we’ll talk about next). True starvation mode is strictly a survival mechanism.
In extreme cases, starvation mode can occur, but it’s unlikely that the majority of people will experience this by dieting. Only when your body starts actually starving will you begin to conserve all your energy to prevent starvation (we’re talking stranded-on-an-island situation). Eating disorders, where calories are drastically restricted for a long time, can also put your body into a true starvation mode.
Intermittent fasting, on the other hand, restricts the window of time when you eat, not the calories or nutrients that you consume in a day. There is no evidence that this type of controlled eating schedule will trigger your body to switch into starvation mode. In fact, short-term fasts may increase the number of calories you burn in a day! Let’s look at how the metabolism is affected by fasting next.
Nada. The dreaded slow metabolism that sabotages your weight loss efforts will not strike while you fast intermittently.
Studies reveal that fasting for up to 48 hours can boost metabolism by 4 to 14 percent! A 16-hour fast with an 8-hour eating window, for example, actually increases how many calories you burn that day—in other words, intermittent fasting speeds up your metabolism!
Here’s how. During a short-term fast, norepinephrine—a hormone that plays a critical role in your metabolism—drastically increases in your blood. Norepinephrine stimulates your metabolism and instructs your body to break down fat for energy. However, if you fast for much longer periods (multiple-day fasts), the effects can reverse, decreasing your metabolism.
Not too much. When intermittent fasting is used for weight loss, it can result in some muscle loss. But here’s the catch—any time you lose weight, you’re losing both fat and muscle. That’s why strength training is so important when you want to lose body fat while maintaining lean muscle mass.
The fact that you can possibly lose muscle mass while intermittent fasting shouldn’t deter you from trying to fast. Instead, focus on minimizing muscle loss because it’s nearly impossible to avoid altogether.
The quantity and quality of your food matter too. Eating enough calories and balancing your macronutrients during your eating window is crucial if you don’t want to deplete your body. Lack of protein is a huge culprit when it comes to muscle loss. Keep protein high, eat filling and satiating meals, maintain a strength training routine, and your muscles will thrive.
Not exactly. It’s important to keep your blood sugar levels in your target range as much as possible. This will help prevent or delay long-term serious health problems, like heart disease, vision loss, and kidney disease. Staying in your target range can also help improve your energy and mood!
Intermittent fasting can lower your blood sugar levels, but this is good news for the majority of us! Over 37 million Americans—about 1 in 10—have diabetes. Millions more have high blood sugar. Intermittent fasting could be the very solution to our country’s blood sugar struggles!
This practice will help you hit that optimal target range. Intermittent fasting has therapeutic effects on blood glucose and significantly improves insulin resistance! Studies argue that it should be used to prevent chronic disease!
If you have diabetes, fasting has the potential of lowering your blood sugar levels too low. On the other hand, intermittent fasting can reduce type 2 diabetes symptoms and even the underlying causes. Intermittent fasting may improve blood glucose levels, insulin resistance, blood pressure, and weight loss. Check with your doctor and ask them about safe ways to fast intermittently.
Nope. A typical 16-hour fast—which is what I recommend—won’t trigger a binge. Drastically restricting how much you eat, however, will likely lead to binges, because nutritional deprivation just isn’t sustainable.
Depriving yourself of food is extremely taxing on your body. Over the long term, it can raise your risk of having problems with blood pressure, cholesterol, and diabetes, among other health issues. Eating enough during your eating window is critical if you want to maintain your health, boost your weight loss, prevent binges, and maximize the benefits of fasting.
No way! Can you guess what the science says? Certain health issues, like infectious diseases, inflammatory bowel diseases, autoimmune diseases, drugs, alcohol, and cancer treatment, can damage the intestines and cause malabsorption.
Fasting, though, actually improves nutrient absorption! That’s why it’s a good idea to take certain supplements on an empty stomach. Evidence suggests that intermittent fasting may benefit your gut health and boost its microbiome!
Want to lose weight without restricting your diet and cutting calories? Grab my free Guide to Intermittent Fasting ebook to get healthy, lose weight, and regulate your hormones!