Signs & Symptoms of Starvation Mode

Restricting calories is key to weight loss, but it's possible to go too far. Dieters have long blamed "starvation mode" for making it harder to shed pounds, though some have doubted its existence. The technical term for starvation mode is adaptive thermogenesis, and it does exist — though it might not always be to blame for weight-loss plateaus.

If you don't eat enough calories for a period of time, your body may go into starvation mode or adaptive thermogenesis. (Image: MirageC/Moment/GettyImages)

What Is Adaptive Thermogenesis?

The concept behind "starvation mode" is simple: When you eat fewer calories, your body worries that it's not going to get more food anytime soon. Your body overcompensates for this potential lack of food by burning fewer calories and holding onto fat stores. Instead of shedding pounds like you want to, you hit a weight-loss plateau.

A University of Cambridge study published in 2017 looked at how mice adapted to restricted calorie consumption and its effect on weight loss. The university noted that mice share physiological and biological similarities with humans, which is why the rodents are beneficial in studying how human bodies work. Researchers identified a group of neurons in the hypothalamus that drive hunger when activated. When there's no food available, however, that group of neurons deactivates and works to restrict energy burn.

Symptoms of Starvation Mode

Although it's necessary to cut back on calories to lose weight, there are some clear signs when you're not eating enough calories. Your body doesn't slip into adaptive thermogenesis after missing just a meal or two. However, after a significant period of time of consistently undereating, you will start to feel the effects, while also noticing that you're not losing any more weight. The signs and symptoms of starvation mode may include:

  • Lethargy. Calories are, essentially, fuel for your body. Therefore, when you don't take in enough fuel, you'll run out of gas. You'll experience this through a lack of energy, decrease in motivation and overall feeling of fatigue.
  • Feeling cold. Calorie restriction lowers your core body temperature according to the journal Aging, so you might be asking for extra sweaters to bundle up if your body has slipped into adaptive thermogenesis.
  • Constipation. Your body needs food to convert into bowel movements. Without that food, particularly the fiber-rich foods such as fruits, vegetables and whole grains, bowel movements will be less frequent and the stools will be harder and painful to expel.
  • Depression. Mental health issues can stem from a variety of causes, which may include nutrient deficiencies. If you're not eating enough and your body has gone into starvation mode, you might not be getting the nutrients that positively affect your mood. This nutrients include omega-3 fatty acids, iron, folate, vitamin D, B vitamins, zinc and iodine.
  • Hair loss. As in the case of depression, hair loss due to a lack of calories is probably a symptom of not getting the proper nutrients that your hair needs to stay healthy. These important nutrients include protein and fatty acids.

Getting Through Starvation Mode

If you think your body truly has hit a weight-loss plateau because you have been restricting calories, you can shake things up to get the numbers on the scale moving again. Although it might seem counterintuitive to weight-loss purposes, you can actually break out of adaptive thermogenesis by increasing the amount of food that you eat. Some ways to do that include:

  • Planning your meals and snacks: Not only does planning your food help remind you to eat regularly, but it also allows you to ensure that you're getting enough of the nutrients you need to avoid the signs of starvation mode. For example, you can plan to incorporate snacks of walnuts and dinners of fatty fish to make sure that you're getting enough omega-3 fatty acids, while planning to eat leafy greens and fortified oatmeal can ensure that you're consuming potassium and magnesium regularly.
  • Eating at regular intervals: Sometimes, you might not feel hungry — that's a symptom of starvation mode. However, if you want to break through a weight-loss plateau and get out of adaptive thermogenesis, you should eat a small meal or snack every three to four hours. Additionally, eating regularly avoids a common pitfall of going too long without food, becoming ravenous and binge-eating later in the day.
  • Adding strength-training to your routine. If you start to lose weight without doing anything to maintain muscle mass, you'll begin to lose that muscle mass along with the fat. Muscle mass is key to keeping your metabolism, or the rate at which your body burns calories, high enough to stay out of starvation mode. General expert consensus recommends strength-training exercises, whether using weight machines at the gym or doing bodyweight exercises such as squats and pushups, at least two times a week.

Risks of True Starvation

There's a difference between adaptive thermogenesis, or starvation mode, and actually starving yourself. The latter is an indication of anorexia nervosa, an eating disorder that's marked by fear of gaining weight and an abnormally low body weight. Anorexia, as it's typically referred to, can create dire health issues that may lead to death, even if the person who suffers isn't yet severely low in weight. Death typically results from heart arrhythmias, or abnormal rhythms, or an imbalance of minerals, such as sodium, potassium and calcium, which are collectively known as electrolytes.

Although death is the worst-case scenario, there are other potential health issues from starving yourself, too. In fact, anorexia can cause damage to every organ in the body, including the heart, brain and kidneys. Additional risks of anorexia include:

  • Osteoporosis, or bone loss
  • Anemia, or extremely low iron
  • Muscle loss
  • Decreased testosterone in men
  • Loss of a period in women
  • Constipation, bloating and nausea
  • Mental health concerns, including depression, obsessive-compulsive disorder, substance abuse, anxiety and suicidal thoughts

People with anorexia often focus intently on controlling their weight and shape, to the point that it interferes with their day-to-day life. If you're worried that you might be suffering from anorexia nervosa or another eating disorder, it's important to reach out for medical help.

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