Starvation Mode: How It Works

We’ve all seen the countless threads and posts about starvation mode. Many contain a lot of misinformation and apply the concept too broadly. It’s my aim to clear up some misconceptions (of both believers and non-believers). I’m going to try to keep this simple and straightforward and easily understandable.

What is Starvation Mode?
Starvation Mode – aka survival mode, famine response, adaptive thermogenesis

Starvation mode is a reaction to inadequate energy. If your food intake is too low to meet energy requirements, the body starts accessing inside sources. It will attempt to access fat stores first, and in the highest proportion. If you have a lot of fat stores, most of the energy will come from fat, and a little from muscle. If you have less fat stores, most will still come from fat, but a higher percentage will come from lean tissue, such as muscles. The leaner you get, the more difficult it is for the body to access fat quickly.

When the body perceives intake to be too low and energy stores (fat) to be inadequate for making up the difference quickly, it begins to compensate to prolong survival. First, it slows metabolism (the rate at which you use energy.) If intake continues to be too low, it then begins to access muscle, because it is easier and faster. The loss of lean tissue further slows metabolism. If this cycle continues for a significant period, at the right levels, it results in an ever-decreasing metabolism. This means a person can eat less and less (to a point), and still have slow or no weight loss because the body’s energy requirements have decreased. Remember that total energy requirements include BMR, daily activity and purposeful exercise.

Who is at Risk?
Most people with large amounts of fat stores are not at risk of starvation mode. This is usually women over 35% body fat and men over 25% body fat, but there is no exact point. They have sufficient energy stores to supplement the body’s needs for energy (however, they still have other needs that must be met, such as vitamins and minerals). The closer a person is to a healthy BMI, the higher risk and consequences of starvation mode.

When Does it Happen?
It doesn’t happen by skipping a meal or even a whole day or at 1200, 1000, or any other random cal number. Typically, metabolism will begin to decrease after about 72 hours of significantly inadequate intake. But this is dependent on the individual’s specific situation – what the energy requirements are, how much fat they have, and the exact level of intake. The loss of lean tissue begins sometime later. It could be days, weeks or months. It may be at 1200 for one person, and 2000 for another. Again, it depends on the individual and will be a different point for everyone.

Then Why are Anorexics Skinny?
Anorexics were “normal” weight at some point. They began decreasing intake and using up fat stores. How long this takes depends, again, on energy requirements and actual intake. The body has a “range” in which it feels comfortable accessing fat, without decreasing metabolism too much or burning too much muscle. As an average, this is between 250 and 1000 calories below maintenance requirements. When you drop below this range, the body begins starvation mode reactions. Anorexics WERE in starvation mode at some point – but they continued to decrease intake. There is a level of extreme calorie restriction and lack of fat stores at which starvation mode turns into actual starvation. The body is adaptable, but it has its limits. At this point, the body has no choice but to burn everything – fat, muscle, organs, hair, skin, etc - simply to sustain bodily functions. Severe anorexia is the result of continuous extreme calorie restriction and malnutrition (typically below 500 cals). You can try it their way. But remember, a lot of them develop horrible diseases from malnutrition and many of them die.

But Some People Claim You GAIN Weight in Starvation Mode?
Starvation Mode itself will not cause weight gain. However, a combination of starvation mode, binges, and carb loading, can cause weight gain. Once the metabolism decreases, your energy requirements are lower. So you have to eat less just to maintain your current weight. The body has become more efficient at using and storing energy. But most people have a hard time maintaining a very low intake consistently for long periods. So if your typical intake is 1000 (just an example), but you have occasional binges of 3000 and the binge is mostly carbs, the body can’t use all of that at one time anymore. So the body shuttles it to fat storage. This won’t be a huge gain, but a lb or two a month maybe. It’s not dramatic, but if someone lives this way for years, they can gain a decent amount of weight.


Further Reading:
http://www.myfitnesspal.com/topics/show/186814-some-mfp-basics
http://www.myfitnesspal.com/topics/show/61706-guide-to-calorie-deficits
http://www.myfitnesspal.com/topics/show/175241-a-personal-view-on-exercise-cals-and-underfeeding
http://www.myfitnesspal.com/topics/show/222019-60-lbs-in-60-days?hl=60+lbs
http://www.myfitnesspal.com/topics/show/3047-700-calories-a-day-and-not-losing
http://www.myfitnesspal.com/topics/show/10589-for-those-confused-or-questioning-eating-your-exercise-calo
http://www.myfitnesspal.com/topics/show/153704-myth-or-fact-simple-math-3500-calories-one-pound-eat
http://www.myfitnesspal.com/topics/show/173853-an-objective-look-at-eating-exercise-calories
http://www.myfitnesspal.com/topics/show/12250-1000-calorie-deficit-not-for-people-with-healthy-bmi
http://www.myfitnesspal.com/topics/show/208407-how-to-repair-a-damaged-metabolism-stavation-mode?page=1#posts-2752820
http://www.myfitnesspal.com/topics/show/187973-an-email-response-that-might-help-some?page=1%23posts-2493477
http://www.myfitnesspal.com/topics/show/8977-your-body-s-thoughts-on-calories
http://www.myfitnesspal.com/topics/show/777-why-is-starvation-mode-so-bad
http://www.myfitnesspal.com/topics/show/49690-the-banks-plan?page=1#posts-541471
http://www.myfitnesspal.com/topics/show/69708-calorie-deficit-for-dummies-a-little-long
http://www.myfitnesspal.com/topics/show/81391-starvation-mode-myths-and-science
http://www.myfitnesspal.com/topics/show/79181-dogmeat-s-thoughts-on-weight-loss