If you’ve ever dieted, you’ve probably been warned of “starvation mode.” You’ve heard that your metabolic rate will slow down and fat loss will stall. You may also have heard that it’s possible to eat fewer calories than you burn and not lose fat.
Maybe a friend or a client has INSISTED that they are doing everything right and creating a calorie deficit, but yet, they CAN’T get the scale (or fat loss calipers) to budge.
If this were possible, it would violate the First Law of Thermodynamics, which says that the energy in a closed system is constant. In simple terms, this means that to lose body fat, you have to take in fewer calories than you burn.
In reality, the people who think they have gone into starvation mode and are violating the First Law of Thermodynamics are not actually creating an energy deficit, probably because they are either:
1) Inaccurately calculating calorie intake or
2) Overestimating how active they are and how much they burn.
There’s boatloads of research showing that humans are notoriously bad at assessing how much they’re eating, how much they’re moving, and what it measures up to calorie-wise.
The Real Definition Of Starvation Mode
There’s another definition of “starvation mode” that is science-based and it is the main reason SO few people successfully lose weight and keep it off. When you lose body fat, the body starts trying to conserve energy by reducing the amount of calories you burn daily.
This makes you feel hungrier because hormone levels that regulate hunger get out of whack. Other biochemical changes occur as well, making you feel lazier and less energetic so that daily physical activity drops.
This phenomenon is very real and very confusing. This article will help you understand it so you can adopt habits that allow you to avoid starvation mode so that you get the body you desire.
The Role Of Resting Metabolic Rate In Starvation Mode
When you lose weight, the amount of calories your body burns a day, known as your resting metabolic rate (RMR), drops significantly. Your RMR is the amount of calories your body burns just staying alive and doesn’t include exercise or any kind of physical activity. It’s made up of the energy required for cognition and organ and heart function.
One side effect of losing fat is that you also lose lean muscle mass. If you’re cutting calories this is pretty much guaranteed to happen. There are ways to minimize the amount of muscle you lose, which will be described below in the Tips section.
The problem with losing lean mass is that muscle is metabolically active and burns a significant amount of calories daily—much more than body fat. Studies show that for long-term diets, for each kilogram lost, people burn 12.8 fewer calories. That means that if you lose 10 kg, you reduce RMR by 128 calories a day.
How Your Biology Responds To Lack Of Calories
Unfortunately, that’s not all the bad news related to starvation mode. Consider a typical scenario in which someone is trying to lose body fat: They attempt to create a calorie deficit by reducing the amount of energy they eat (decreasing calories in). They may also exercise, which increases calories out. The body releases calories from fat tissue and they lose body fat. Hooray!
But, the body doesn’t experience this as a good thing. It experiences the lack of calories as a huge threat. The brain receives signals via changes in hormone levels that energy stores (body fat) and nutrient availability (incoming calories) are reduced. The brain takes immediate action to reduce calories out by slowing metabolic rate and making you less active.
An example is a recent study that looked at metabolic adaptations following massive weight loss in two populations: participants in the Biggest Loser TV show and subjects who had bariatric surgery. Both groups lost between 40 and 50 kg by the end of the study. RMR decreased significantly more than expected based on measured body composition changes.
Other studies show a similar disproportionate reduction in metabolic rate from weight loss. One study found that when subjects lost 10 percent of body weight, metabolic rate dropped by 15 to 25 percent.
Scientists believe this response is the body’s natural protective mechanism developed through millions of years of evolution to keep you from starving when food was something you had to work to get. The following are some of the factors that contribute to metabolic adaptation.
Adaptive Thermogenesis Reduces Physical Activity
Studies show that sometimes when we lose weight, we get lazy. We have less biological drive to be active and tend to move less. This plays out in real life when people choose to take the elevator, drive more, or stay sedentary for longer periods. They may take fewer walks or skip their workouts.
Scientists think that a network of neurotransmitters called the orexin system get altered, which reduces activity levels and triggers food intake. In simple terms, we are sleepier and more sluggish. These pathways can be overcome consciously, but they have a powerful effect on unknowing dieters who are trying to sustain weight loss.
Fat Loss Increases Work Economy—You Get More Efficient At Doing Work
Another thing that happens is that your body becomes more efficient at doing work, which is a good thing, but unfortunately, it means that fewer calories are burned to do the same amount of effort.
Less total muscle mass must be moved during physical activity, so the activity will be less energetically expensive. For example, if you burned 200 calories doing a weight lifting workout when you weighed 165 pounds, you might only burn 170 calories if you lost 10 pounds and weighed 155 pounds.
Lower Body Mass Means Lower Thermic Effect
When you eat, it costs the body calories to digest and assimilate food. You probably know that protein is the most costly food, requiring the body to burn about 25 percent of the calories supplied in a meal of pure protein just to digest it. This is called the thermic effect of food and it’s highest for protein, followed by carbs and then by fat. When you cut calories to lose fat, the body has less food to process so the thermic effect goes down and calorie burn is reduced.
Hormones Affect Metabolic Rate
The hormones leptin and insulin both reduce hunger messages in the brain. Leptin is secreted from fat tissue. When you have a lot of body fat, leptin will be higher and send an appetite-suppressing message to the brain so that you eat less.
Insulin will also be lower when you cut calories and lose body fat, mainly because smaller fat cells are more sensitive to insulin, so less is needed for the same degree of metabolic control. Scientists think that low insulin sends a message of “depleted energy” to regulatory areas of the brain.
Unfortunately, studies show that when people lose body fat, leptin and insulin are reduced to a greater extent than would be expected by the amount of fat loss. In one recent study, overweight men and women lost an average of 10.7 percent body weight after dieting for 8 weeks. Instead of leptin dropping by a similar amount, it was reduced by a whopping 48 percent.
Even though these subjects had lost fat, they were still overweight and had significant fat stores to burn before reaching a healthy weight. However, the body didn’t experience it that way. Instead, there was a mismatch between the message the brain receives (that energy stores are low) and the amount of body fat actually available.
The disproportionate drop in leptin and insulin translates into increased hunger and higher food intake. People often report “obsessing” about food, which scientists believe has to do with changes in the brain such that when we are exposed to sensory food images, such as pictures of food on TV or when our co-workers order pizza, we experience increased motivation and drive to eat. Over time, this results in an increase in calories so that we gain fat.
Five Tips To Avoid Metabolic Slowdown
Be aware that adaptive thermogenesis is a completely normal physiological response to a sustained lack of calories. What follows are a couple of key habits that can make a big difference and help you avoid starvation mode.
#1: Lift Weights
Exercise works wonders for maintaining muscle mass when losing fat. Lifting weights is your best exercise option because its main target is to trigger protein synthesis. Use a progressive program that includes phases of moderately heavy weights with higher reps and shorter rest periods for the greatest preservation of muscle mass.
#2: Increase Protein
Protein foods trigger protein synthesis, which maintains muscle mass in the body when losing fat. One study found that a protein intake of 1.6 g/kg sustained lean mass in conjunction with weight training in lean subjects who were put on a calorie-restricted diet.
#3: Try Carb Cycling
Carb cycling is a method for creating an energy deficit but it avoids the sustained long-term calorie restriction that alters hormones and is the main culprit in producing starvation mode. It involves following a low-carb, high-protein diet most of the time, but every 5 to 7 days, you increase your carb (and calorie) intake significantly.
This method is effective because low-carb, high-protein diets are naturally satiating so that people automatically reduce calories without even trying. This helps them avoid hunger and cravings. Then, the high-carb day allows for restoration of muscle fuel stores, keeps the body sensitive to insulin, and provides abundant calories so that the body doesn’t downregulate RMR.
#4: Stop Counting Calories
If you’ve been eating very low calorie (below 1,200 for women and 1,600 for men) for a long time, it’s time to stop counting and increase your calorie intake. To knock your body out of starvation mode, you need to provide enough energy so that it senses that fuel stores abundant. It will respond by improving hormone levels and increasing metabolic rate.
#5: Make A Conscious Effort To Be As Active As Possible
Instead of worrying about spending a longer period of time at the gym, keep your workouts short but intense and focus on increasing your non-exercise-based physical activity. Frequent, spontaneous movement will upregulate your metabolism and contribute to better blood sugar management and insulin sensitivity.
Make it happen by using active forms of transportation (walking, cycling, taking the stairs). Limit leisure screen time in favor of physical activity that is fun and relaxing—try yoga or a martial art. A pedometer is another option—active people have no problem surpassing the recommended 10,000-step mark.