If a list of nutritional urban legends existed, the idea that your body can easily slip into starvation mode would be high up there. Drilling down a bit, I'm specifically talking about the often-repeated belief that if you limit your caloric intake (or even fast) for a day or several days, your metabolism is going to take a hit because your body goes into so-called "starvation mode" and does everything it can to preserve energy.
Here's the deal: When you read or hear about this concept, it's usually because someone is trying to explain why dramatically cutting calories to lose weight is a bad idea. The starvation mode theory holds that crash-dieting isn't just dangerous, but it's also counterproductive. You're trying to lose weight, but you're actually slowing down your metabolism, which makes it even harder to accomplish your goals! Unfortunately, the idea that crash-dieting will slow your metabolism, while well intentioned, isn't really an accurate read of the science. I'll talk about why in more detail. But also, something else I'm going to talk about: Crash-dieting or yo-yo dieting or dramatically cutting calories for the sake of weight loss is definitely still a bad idea, and also counterproductive. Just...not because of the metabolism thing. Let's get into it.
Look: "Starvation mode" is definitely real. The confusion comes in because the term means many different things to many different people.
The concept of starvation mode is confusing because, yes, it is a thing—if you don’t eat enough, in response to the low intake of fuel, your body will likely store calories it would otherwise burn. But starvation mode isn’t an ever-present threat lurking around every corner, just waiting for you to skip a meal so it can kick into gear and mess with your metabolism.
“A lot of times people think they’re going into starvation mode when they skip a meal or fast for a day, and that’s truly not the case,” Philadelphia-based Joy Dubost, Ph.D., R.D., tells SELF. Unless someone has a prolonged, dire lack of access to food or an eating disorder like anorexia, it’s very hard to go into what Dubost describes as “complete clinical starvation mode.”
Rachele Pojednic, assistant professor in the nutrition department at Simmons College and staff scientist at Beth Israel Deaconess Medical Center, agrees. “There’s a difference between the popular perception of starvation mode with regard to diet culture and actually being starving,” she tells SELF.
When a person has been eating a low-calorie diet for long enough to actually be starving—there’s no specific caloric threshold or length of time for this to happen because it’s so individual, the experts explain, but it certainly takes longer than a day without food—a few physiological processes take place.
For starters, your insulin and glucose levels can get thrown out of whack. Insulin is a hormone that shuttles glucose (blood sugar) from the bloodstream into the body's cells, where's it's stored as glycogen for later use as energy. When insulin is low, that keeps the glucose in your blood. This happens in the case of starvation so that you have more blood glucose available for quick energy, Pojednic explains. Your body will also start to increase a process known as lipolysis, or breaking down fat to release fatty acids for energy. In addition, you’ll break down protein reserves, usually muscle, for another energy source, Dubost explains, and undergo large mineral losses that affect your body’s electrical systems, like your heart. Symptoms of all of this can include weakness, apathy, memory lapses, and muscle cramps.
“It’s really hard, if you have adequate access to food, to put yourself into this mode because you are always going to be able to eat something eventually,” Pojednic says.
Although randomly skipping meals isn’t good for you, doing it every so often won’t catapult your body into starvation mode.
Experts tend to recommend eating every three to four hours for optimal energy and health. Starvation mode happens over the long-term, so skipping a meal every once in a while won't permanently affect your metabolism. Haphazardly skipping meals can still affect your weight in another way, however.
“The tendency on the other end of [skipping meals] is to overcompensate,” Pojednic says. “You’re not going to go and eat a well-balanced healthy meal—you’re probably going to go eat something that’s not particularly good for you, or it’s a massive portion.” It can also make you hangry, which is bad news.
Fascinatingly enough, some research shows that skipping meals in the form of intermittent fasting (IF) a structured method of alternating days of eating less (or nothing) with days of eating normally or having whatever you want, might be beneficial for health and weight loss. “There's interesting emerging science on intermittent fasting and calorie restriction,” Pojednic says.
The research is limited, but when done properly, intermittent fasting looks promising for weight loss. For example, a 2015 review in Molecular and Cellular Endocrinology analyzed 40 studies of intermittent fasting and found that people lost 7 to 11 pounds over 10 weeks of IF. Many of the studies involved fasting periods between one and seven days, but it's worth noting that most people who practice IF alternate days of fasting with days of eating, or fast one or two days a week and eat regularly the rest of the time.
Depending on the length of a fast, it can be severe enough to cause starvation mode. But the theory is that either way, people who do intermittent fasting still end up eating fewer calories overall, thus avoiding weight gain.
That doesn't mean you should structure an intermittent fasting plan for yourself—if you're interested in trying this out, it's best to talk to a doctor or registered dietitian first. (And if you have an eating disorder, you should always check with your doctor before changing your eating habits.)
With that said, something like severe yo-yo dieting or calorie restriction can slow down your metabolism over time.
Yo-yo dieting involves repeatedly gaining and losing weight, usually due to going on and off of intense diets. In the long-term, this practice, or just consistently eating too few calories for your body can mess with your metabolism. “I see people trying to take their calorie intake down below 1,000 calories per day, and this can be very harmful to their metabolism, as well as their health overall,” Pojednic says.
When you lose a lot of weight, your metabolism automatically slows down because your body needs less energy to function. When you start eating normally again (or overeating), you’re working with a lower metabolism, which can lead to weight gain, especially if you passed your own personal starvation mode threshold and your body now wants to get as much energy as possible. “Your body is trying to conserve whatever it can,” Dubost says. This process only intensifies as you get older and your metabolism naturally slows, she adds.
There’s no easy way to determine what level of yo-yo dieting or calorie restriction will result in metabolic changes, Dubost says—it all depends on your individual body. However, experts generally recommend that women don’t eat fewer than 1,200 calories a day to avoid undereating. And if you're very active, you may need hundreds more calories than that to prevent undereating, although that varies widely depending on your activity level.
Yo-yo dieting or otherwise severely restricting calories are both bad ideas in general, not just because they can mess with your metabolism. Depriving yourself of food is taxing on your body, and over the long-term, it can raise your risk of having problems with blood pressure, cholesterol, and diabetes, among other health issues. It will also likely lead to binges, because it just isn't sustainable. Instead, if you're trying to change any eating habits you may have, making small lifestyle tweaks that you can actually stick to is the best way to go about it. That way, you avoid the awful feelings that can come about when you're forcing yourself to eat less than you need: crankiness, unhappiness, and straight up misery. There's no need to treat yourself that way!
There are a couple of things you can do to keep your metabolism running as smoothly as possible.
Paying attention to your hunger cues is key. “It’s not only about eating when you are feeling that urge,” Pojednic says. “The flip side is paying attention to when you’re full and eating only enough until you feel like you’ve been satiated.”
Given our easy access to delicious food, this can be easier said than done. Mindful eating can help. So can eating high-fiber foods like whole grains, fruits, and vegetables, along with foods rich in protein and healthy fats—all of these will help fill you up and boost your health.
When it comes to being active, strength training is a great way to build muscle, which is more metabolically active than fat, meaning that adding muscle mass can help keep your metabolism high. If you don't have much muscle, your body doesn't require as much energy to function, so your metabolism doesn't need to work as hard. But it's not just about strength training. Being active in general is extremely important for your health, so it's important to find a workout method you love, Dubost says.
This story originally appeared on Self.
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