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Is "starvation mode" real or a myth?

Ist der “Hungermodus real oder ein Mythos?

Weight loss is generally seen as a positive thing. It can improve health and appearance and bring all kinds of physical and mental benefits. However, your brain won't necessarily see it the same way. Your brain is more concerned about preventing you from starving yourself and will do everything it can to make sure you (and your genes) survive.

If you lose a lot of weight, your body will start to conserve energy and reduce the amount of calories you burn (1). It will also make you hungrier and lazier and increase your cravings for food. This can cause you to stop losing weight and feel so miserable that you give up your weight loss efforts and put the lost weight back on.

This phenomenon is often referred to as starvation mode, but it's really just your brain's natural mechanism to keep you from starving yourself. Fortunately, there are a number of things you can do to prevent this from happening so that you can continue to lose weight without torturing yourself in the process.

But before we get to that, let me first explain what starvation mode is and how it works.

What does 'starvation mode' imply?

What most people refer to as 'starvation mode' (and sometimes 'metabolic damage') is the natural response to long-term calorie restriction. This involves the body's response to reduced calorie intake by reducing calorie expenditure in an attempt to maintain energy balance and prevent starvation.

This is a natural physiological response and is not really controversial. It is widely accepted by scientists and the technical term for it is "adaptive thermogenesis" (2). I will use the term starvation mode in this article, even though this term is inaccurate, as true starvation is something that is almost completely irrelevant in most weight loss discussions.

Starvation mode was something useful in our evolutionary past, but does more harm than good in our modern age where overweight and obesity are out of control.

Calorie intake and calorie expenditure

Obesity is a disorder caused by an excessive accumulation of energy/calories. The body stores energy (calories) in its adipose tissue for later use. When more calories enter adipose tissue than calories leave adipose tissue, we build up fat. If more calories leave the adipose tissue than enter it, we lose fat. This is a fact.

Pretty much all weight loss diets cause a reduction in calorie intake. Some do this by directly controlling calorie intake (by counting calories, weighing portions, etc.), while others reduce appetite so that people automatically eat fewer calories. When this happens, the amount of calories leaving the fat tissue exceeds the amount of calories entering the fat tissue and we lose fat.

However, the body does not see this in the same way as you do. In many cases it sees this as the beginning of starvation. For this reason, it starts to fight against this and does everything it can to prevent you from losing fat.

The body and brain can respond by making you hungrier (so you eat more and increase calorie intake), but what is most relevant to this discussion is what happens to the amount of calories you consume. Starvation mode implies that your body is reducing calorie consumption to try to restore energy balance and prevent you from continuing to lose weight despite a calorie deficit.

This phenomenon is very real, but whether this response is so strong that it can actually prevent you from continuing to lose weight or even starting to gain weight despite continued calorie restriction is debatable.

Summary: What is commonly referred to as starvation mode is the body's natural response to prolonged calorie restriction and involves a reduction in the amount of calories your body burns, which can slow down your weight loss.

The amount of calories you burn can change

The amount of calories you burn throughout the day can be broken down into four areas:

  1. Basal metabolic rate: this is the amount of calories your body uses to maintain its basic vital functions such as breathing, heart rate and brain function.
  2. The thermic effect of food (TEF): The calories used during the digestion of food. This usually accounts for about 10% of calorie intake.
  3. The thermic effect of exercise (TEE): The calories burned during physical activities such as exercise.
  4. Non-exercise-induced thermogenesis: Calories burned by "fidgeting", changes in body position, etc. These activities usually occur unconsciously. These activities usually take place unconsciously.

Calorie expenditure in all four of these areas can decrease as you reduce your calorie intake and lose weight. This includes a reduction in exercise (both conscious and unconscious), as well as major changes in the nervous system and various hormones (2, 3). The most important hormones in this context are leptin, thyroid hormones and norepinephrine, all of which can decrease in the context of calorie restriction (4, 5).

Summary: There are several ways in which the body burns calories. All of these can be reduced in volume if you reduce your calorie intake over a longer period of time.

Studies show that calorie restriction can reduce calorie consumption

Studies have clearly shown that losing weight reduces the amount of calories you burn (6). According to a large study review on this topic, this amounts to 12.8 kcal for every kilogram of weight you lose (7). So if you lose 20 kilograms of weight, you will burn about 250 kcal less per day.

However, this reduction in calorie consumption can be far greater than predicted purely on the basis of weight changes. For example, some studies show that losing 10% body weight can reduce the amount of calories burned each day by 15 to 25% (8, 9).

This is one of the reasons why weight loss tends to slow down over time and why it is so difficult to maintain the lower weight achieved. The latter may well require you to eat fewer calories for the rest of your life.

In this context, keep in mind that this reduction in metabolic rate may be even more pronounced in some groups, such as postmenopausal women, who find it difficult to lose weight.

Muscle mass tends to decrease

Another side effect of weight loss is that the amount of muscle mass also tends to decrease (10). As you may know, muscle mass is metabolically active tissue that burns calories around the clock.

However, the reduction in calorie consumption is greater than can be explained simply by a reduction in muscle mass alone. The body becomes more efficient at doing work, so less energy is needed to do the same amount of work (11).

Calorie restriction therefore makes you burn fewer calories for the physical activities (whether they are conscious or unconscious activities) that you perform.

Summary: Weight loss and reduced calorie intake can lead to reduced calorie expenditure. This adds up to an average of 12.8 kcal per kilo of weight lost per day.

How you can prevent a reduction in metabolic rate

Keep in mind that a slowdown in your metabolic rate is nothing more than a simple, natural reaction of your body to a reduced calorie intake. As such, some level of reduced calorie consumption will be unavoidable, but there are a number of things you can do to mitigate these effects.

Train with weights

By far the most effective measure you can take is to perform resistance training. The obvious choice would be to train with weights, but bodyweight-only exercises can also work.

Studies have shown that resistance training, where your muscles have to exert force against resistance, can have great benefits during a diet. In one study, 3 groups of women were put on an 800 kcal diet. One group did no training, one group did aerobic training (cardio) and the third group did resistance training (12).

Both the group that did not exercise and the group that performed aerobic exercise lost muscle mass and showed a significant reduction in metabolic rate. However, the women who did resistance training were able to maintain their metabolic rate, muscle mass and strength levels.

This has been confirmed by many other studies. Weight loss reduces muscle mass and metabolic rate and resistance training can (at least partially) prevent this (13, 14).

Keep your protein intake high.

Protein is the most important macronutrient when it comes to weight loss. A high protein intake can both reduce appetite (and therefore calorie intake) and increase metabolic rate (and therefore the amount of calories burned) by 80 to 100 kcal per day (15, 16).

In addition, a high protein intake can reduce cravings and the urge to eat late at night, leading you to eat hundreds of calories less per day (17, 18). Keep in mind that this involves increasing your protein intake without consciously restricting anything else.

Your protein intake is also important to reduce unwanted side effects of long-term weight loss. If your protein intake is high, your body will be less inclined to break down muscle for energy. This can help maintain your existing muscle mass, which can at least partially prevent a reduction in metabolic rate associated with weight loss (18, 19, 20).

Taking a diet break can help

Some people routinely take so-called refeeds, where they break their diet for a few days. On these days, they eat slightly more calories than they consume and resume their diet a few days later.

There is evidence that this can temporarily increase levels of hormones such as leptin and thyroid hormones, which tend to fall during prolonged weight loss (22, 23).

It may also be useful to take longer breaks of a few weeks. However, you should make sure that you eat consciously during these breaks. Eat your maintenance calorie intake or slightly more calories, but don't increase your calorie intake so much that you start to gain fat.

Be prepared to gain a few pounds from the extra food and increased water weight. This is nothing to worry about as you will lose the weight quickly if you continue your diet.

Summary: Training with weights and a high protein intake are two scientifically proven ways to prevent muscle loss and a reduction in metabolic rate during weight loss. A short break in the diet can also be useful.

A weight loss plateau can be caused by many things

When people start dieting, progress can be quite rapid at the beginning. During the first weeks and months, weight will drop without much effort. Later on, however, progress will slow down. In some cases, weight loss can slow down so much that several weeks can pass without any visible changes on the scales.

Such a weight loss plateau can have many different causes (and solutions) and it does not necessarily mean that you are not losing weight. Water retention, for example, can give you the impression that you are not losing any more body fat.

Starvation mode is real

Starvation mode is real, but its effects are nowhere near as strong as many people might think. It can slow down your weight loss over time, but it won't cause you to gain weight despite calorie restriction.

It is also not an "on and off" problem as some people seem to think. Rather, starvation mode represents a whole spectrum of adaptations the body makes to reduced or increased calorie intake.

The term starvation mode is a terribly inaccurate term. Something like "metabolic adaptations" or "slowing metabolic rate" would be much more appropriate. In purely technical terms, this phenomenon is simply the body's natural physiological response to a reduced calorie intake. Without these adaptations, humanity would have died out thousands of years ago.

Unfortunately, at a time when excessive food intake is a much greater threat than starvation, this protective mechanism can do more harm than good.




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