Many diets encourage you to eat fewer calories to lose weight. And with intermittent fasting gaining popularity, you might be wondering what can happen to your metabolism if you restrict calories either short or long-term.

In fact, the term starvation mode might come to mind. Will starvation mode destroy your metabolism and sabotage your weight loss goals?

Starvation mode, adaptive thermogenesis, and metabolic damage refer to changes in your metabolic rate that can result in reduced energy expenditure, difficulty losing body fat, and even cause you to gain weight.

But there’s some nuance to starvation mode and keeping your metabolic rate healthy.

In this article, you’ll learn all about the myths and facts behind long-term caloric restriction, if starvation mode is as damaging as people claim, and what to look out for when it comes to keeping your metabolism healthy.

You’ll also learn the difference between restricting caloric intake long-term and healthy intermittent fasting. Plus, how to navigate weight loss, fasting, and more without hitting a weight loss plateau.

What is Starvation Mode?

Starvation mode is one name for your body’s natural response to a severe caloric deficit.

Because your brain and body are more interested in long-term survival than losing body fat, eating too few calories can act as a starvation signal. As a result, your body may put the brakes on fat loss[*].

The scientific name for starvation mode is “adaptive thermogenesis”[*]. During adaptive thermogenesis, your cells, central nervous system, and hormones work together to reduce your metabolism and stabilize your body weight[*][*][*].

Staying in starvation mode long-term can result in serious hormonal imbalances, extreme difficulty maintaining a stable body weight, and health problems[*][*]. Some people call these harmful effects “metabolic damage.”

Metabolic damage involves disruptions in hunger hormones, loss of lean muscle mass, and — in severe cases — organ damage.

Researchers have documented the occurrence of hair loss, diabetes, and heart failure due to metabolic damage from long-term, very-low-calorie diets[*][*][*].

Is Starvation Mode Real?

While starvation mode is a real thing, people often use the term loosely. As a result, you may have encountered some misconceptions about starvation mode.

Here are some starvation mode myths that you don’t need to worry about:

  • Some people think you can go into starvation mode by missing a meal or trying intermittent fasting — false[*].
  • Likewise, you don’t need to eat lots of tiny meals each day to prevent starvation mode.
  • Difficulty losing weight doesn’t necessarily mean you’re in starvation mode. Weight loss can be challenging all by itself, and you may be making other common ketogenic diet mistakes.

There isn’t a precise formula that can tell you whether a diet will put you into starvation mode, but you can look for warning signs.

4 Warning Signs You’re in Starvation Mode


#1: You Feel Hungry Constantly

Hunger is a normal part of weight loss. If you’re in the process of losing body fat, it’s perfectly normal to feel hungry when you wake up, between meals, before bedtime, or while you’re fasting.

Or, if you just started keto, you may not be fat-adapted yet, which can result in short-term cravings and hunger.

But if you feel hungry constantly, or you’re still hungry after finishing meals, you’re probably close to starvation mode. Severe under-eating and constant hunger are counterproductive because they make it difficult to stick with your diet.

Over time, excessive hunger can also lead to binge eating and unconscious overeating, which can derail your results.

#2: You’re Losing Muscle Mass

If your goal is to lose weight, there’s an enormous difference between burning fat and losing lean muscle mass. When you pursue weight loss at any cost, the likely result is that you’ll lose lean muscle mass instead of burning fat.

Losing healthy muscle is counterproductive for fat loss and doesn’t enhance your appearance, improve your health, or reduce your risk of disease. The lower your calories go long-term, the more lean body mass you’ll lose, and the more your metabolism slows down. It can be a vicious cycle.

During authentic fat loss, your waist circumference and other areas where you carry excess body fat will decrease in size. Your clothes will fit better.

In contrast, losing muscle mass can actually make you look less slender because your shoulders, glutes, arms, and thigh muscles will lose their shape and tone.

Depending on your body type, it isn’t always easy to tell whether you’re losing muscle mass, but taking progress photos can help. If you really want to be on the safe side, you can have your body composition measured using a DEXA scan or the caliper method two or three times per year.

#3: You’re Tired and Irritable

Prolonged periods of severe calorie restriction lead to fatigue and irritability. Everyone has bad days, but if you’ve had a bad week, month, or year, your diet could be at the root of your problems.

When you undereat, your body responds to the threat of starvation by adjusting thyroid hormones, cortisol, and neurotransmitters like dopamine and adrenaline to help you conserve energy and encourage you to look for food[*][*][*].  

As a result, you’re more likely to feel tired and grouchy.

Under-eating also increases inflammation in your brain and adversely affects your sleep, leading to mood issues and a lack of focus[*][*].

#4: Your Exercise Performance is Suffering

When you eat too few calories, your body can’t repair itself, and your exercise performance suffers. If you’re getting less physically fit as you lose weight, consider it a warning sign that you aren’t eating enough.

Increasing your strength levels and aerobic fitness requires sufficient calorie intake to fuel your performance and recover from exercise.

Undereating deprives your muscles and organs of much-needed nutrients and creates hormone imbalances, leading to poor performance[*].

If you’re excessively sore, falling behind on exercise performance, or experiencing signs of overtraining, it’s time to take a closer look at your diet.

5 Tips to Avoid Starvation Mode


#1: Stay in Fat-Burning Mode

While eating fewer calories is one aspect of losing weight, the only way to ensure your body burns fat is to crank up your fat oxidation capacity. If you’re having trouble losing weight, you may not be fat-adapted.

The best ways to improve fat-burning are to follow a low-carb, high-fat diet, engage in intermittent fasting, and perform low- to moderate-intensity exercise a few times per week.

When you eat carbs or exercise too strenuously, your body switches to sugar for its fuel, which is counterproductive for losing fat[*][*]. However, by using fat as fuel, you can avoid starvation mode by relying on your body fat stores.

#2: Eat Nutrient-Dense Foods

In addition to too few calories, inadequate vitamin, mineral, and micronutrient intake can also trigger starvation mode. Your body requires these essential nutrients to function and repair itself. Nutrient deficiencies in your diet can lead to excessive hunger, tissue breakdown, and health problems.

That’s why you should be sure to include a diverse range of nutrient-dense foods in your fat loss diet. Luckily, as opposed to calorie-dense processed foods that are low in nutritional value, there are plenty of nutrient-dense keto-friendly foods to choose from on the keto diet.

#3: Use Ketones and Medium-Chain Triglycerides (MCTs)

Starvation mode usually occurs when your brain senses low energy intake, at which point it signals to your body that there’s a major risk of starvation.

Because your brain consumes about 20% of your overall energy needs each day, it’s vital to fuel your brain to prevent starvation mode[*].

You can use exogenous ketones and medium-chain triglycerides (MCTs) to reach ketosis faster and avoid starvation mode[*]. Even if you aren’t fat-adapted yet, ketones and MCT oil or powder supplements can reduce your appetite, boost fat oxidation, and provide your brain with much-needed energy[*][*][*].

#4: Eat Enough Protein

Eating sufficient protein during weight loss reduces your appetite, prevents cravings, boosts your metabolism, and enables your body to recover after exercise[*][*][*][*].

In addition to keeping you nourished and increasing the number of calories you burn, a relatively high protein intake also helps preserve your lean muscle mass[*][*][*].

Most keto diets include about 20% protein, which translates to 75 grams of protein per day for a 1500 calorie diet, or 100 grams for a 2000 calorie diet.

Check out the keto macronutrient calculator to dial in your macros and ensure you’re getting enough protein. You can also experiment with 25% or 30% protein intake on keto.

#5: Lift Weights

During fat loss, lifting weights and other forms of resistance training — like bodyweight exercises — can stabilize your metabolism, preserve muscle mass, and enhance fat-burning[*][*][*].

Strength training can’t rescue you from starvation mode all by itself, but it’s an excellent choice to improve your weight loss results.

It’s also a great way to learn if your diet is on track. If your performance is getting better every week, you’re definitely not in starvation mode.

However, eating enough protein and calories is essential to ensure recovery and prevent overtraining. If you are under-eating, lifting weights could create more problems than it solves.

How to Avoid Metabolic Slowdown and Repair Your Metabolism

Staying in starvation mode too long can result in metabolic slowdown, also called metabolic damage. Damage to your metabolism occurs due to imbalances in metabolic and hunger hormones and the loss of muscle mass.

The best way to avoid these issues is to stay out of starvation mode in the first place. But if you find yourself unable to shed fat after using a low-calorie diet, here are the best ways to repair your metabolism.

Reset Your Metabolism for Three Months

If your metabolism is damaged, a three-month period of eating maintenance calories will help you regain muscle mass and balance your hormone levels.

The ketogenic diet is a perfect choice for this because it’s filling, nutritious, and allows you to eat ad libitum (according to your appetite) without gaining unwanted fat[*].

You can still exercise for health purposes during the reset period, but remember: the goal during this time is not to lose fat–it’s to repair your metabolism.

Set Realistic Goals and Monitor Your Results

Once your three months are up, it’s time to take a look at your weight loss goals. While it’s possible to lose one to two pounds per week, losing a half pound to a pound every one to two weeks is much more realistic — not to mention healthy and sustainable.

You can resume your fat loss journey by adding more exercise, eating two or three meals per day without snacking, and weighing in once every week or two.

Reframe your definition of success: any reduction in body weight or waist circumference since your last weigh-in is a win.

Take Maintenance Breaks and Hold Off on Fasting and Calorie Restriction

Should you hit another plateau, try taking a 2-4 week break from fat loss. Stay keto, but focus on eating healthy foods at maintenance calorie levels, then get back to fat loss.

If your metabolism was damaged in the past, you need to save intense approaches like intermittent fasting and low calorie intake for the final ten to fifteen pounds of fat that you intend to lose.

There’s good evidence that a very-low-calorie keto diet can be effective, but it’s best to think of this tactic as a sprint across the finish line — not for long periods[*][*][*]. In the meantime, pace yourself, so you don’t burn out early.

The Takeaway: Starvation Mode is Real

No matter what you choose to call it, starvation mode is real. It’s just not quite as common as many people think.

You can restrict calories for a period of time here and there to lose weight without damage to your metabolic rate.

The best solution for starvation mode is to avoid it altogether. If you are perpetually hungry, find yourself losing muscle mass, have less energy than normal, or notice reductions in your physical fitness, it’s time to revamp your eating habits.

By eating nutrient-dense foods, harnessing ketosis, and lifting weights, you can lose fat successfully, build muscle, and prevent starvation mode.

If you’ve already experienced the metabolic slowdown that accompanies starvation mode, you’re not alone. The good news is that you can still shed your excess body fat if you reset your metabolism, set realistic goals, pace yourself, and take breaks when necessary.

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