“Starvation Mode” Explained: Can you REALLY gain weight from eating too little?

Let’s just say you have a history of dieting, but you keep finding yourself either gaining weight or playing tug-of-war with the same 20 pounds on the scale. You go see a Nutrition Professional and after you tell them your story, they say you're not eating enough (WHAT?!) and that you are gaining weight because your body's in "starvation mode.” You leave more confused than when you came in, and you cannot possibly believe that you’re not eating ENOUGH if the scale keeps going up. You gain weight because you eat more than you expend, right? “Calories in vs. calories out” is what we have heard all our lives, is it not??? 

Let me explain…

FIRST OFF- “Calories in vs calories out” IS what weight gain and weight loss ultimately come down to. However, this drastically oversimplifies the science of metabolism and it makes us think that if we just “eat less and move more” then the scale should tip in our favor. The thing about metabolism is that your metabolism (or how much energy you burn; so the “calories out” part of that equation) is a sum of the energy expended from ALL chemical reactions in the body. Everything from how cold your house is, how much water you have had to drink, what food you eat, if you’re fighting a cold, how much stress you are under, how much sleep you had, etc. can change your metabolic demands each day. So to put it simply, the “calories in + calories out = weight change” equation may SEEM simple, but smart watches, apps, and even smart/qualified coaches can’t give you a fully accurate number of how many calories you need or are estimated to burn each day. Sure, we can estimate your RANGE of calories needed to get you where you want to go and be accurate enough to get you results, but it normally takes some trial and error as we learn what your individual body needs. 

SECONDLY- The coaches/people going around saying "starvation mode" isn't real are saying that you can't "gain weight by eating too little." This IS true.

However, they're missing the point: 

"Starvation mode" has become the slang term for "adaptive thermogenesis".

I prefer to call this “adaptive metabolism” because, adaptive thermogenesis is this: " the regulated production of heat in response to environmental changes in temperature and diet, resulting in metabolic INEFFICIENCY" (Joosen & Westerterp). Basically “metabolism” is a fancy word for “all of the chemical reactions in the body needed to keep you alive.” Every time a chemical reaction takes place in your body, heat is produced as a byproduct. The more your body has to do to keep you alive, the more heat produced and the “higher your metabolism” because it is having to do more to keep you functioning optimally. Our bodies are really smart though, and sometimes our bodies have to adapt in order to keep us alive. If our bodies are forced to adapt for too long, they can change up how they function to actually LOWER the demands on the body in order to keep your most vital systems and organs working. Any time this happens, the body cannot function OPTIMALLY. So while your body may need less energy (calories) to keep you alive, you will not be functioning at 100%.

We see the body’s ability to adapt its metabolism in a POSITIVE WAY in any place where food is scarce and people’s bodies are forced to routinely make do on little food. Their bodies down-regulate energy needs (compromise different processes in the body, decrease different demands, and operate sub-optimally overall) in order to SURVIVE. This is how we get the nickname: "survival or starvation mode."

As for where this affects weight gain and stubborn weight loss, we see this in over-fed populations in the form of NUTRIENT deficiencies, like the United States. We essentially have the opposite (but also same) problem:

We're over fed, and undernourished (AKA too many calories, not enough bioavailable vitamins and minerals) and our bodies STILL down-regulate energy needs because we don't have the NUTRIENTS to operate optimally. Basically our bodies are getting more ENERGY than they need, but still having to compromise all over the place.

This is where someone gains weight as a result of this phenomenon:

1. someone is nutrient deficient and generally doesn't eat as much as they need to in order to function optimally

2. Their body, after a long period of eating this way, begins to compromise and down-regulate its energy (calorie) needs 

3. Said person then regularly has days (usually weekends) where they eat more calories than normal (hence they get into an ever-growing calorie SURPLUS = GAIN WEIGHT). 

4. This happens over and over until the food deficiency/nutrient deficiencies are fixed. 

(***No, you should not jump to supplementation for a quick-fix- this might do more harm than good) 

So how do we escape the cycle?

Until there is a lifestyle shift where the body is retrained to get enough food, nutrient needs are met for a significant amount of time, and the body can re-adapt to this new way of life, your body will likely resist weight loss. Keep in mind, if there are nutrient deficiencies present but we know you are not getting enough calories and/or a food in general, then it is as much a FOOD deficiency as it is a nutrient deficiency.

If a health expert has mentioned “starvation mode” to you, there is a good chance they also talked to you about doing a Reverse Diet. Basically a reverse diet is a slow, strategic increase in the amount of food and nutrients you eat each day with the goal of helping your body readjust to getting enough nutrients for optimal functioning. There is mixed research on the effectiveness or even the necessity of reverse diets. What we do know for sure though, is that the human body is incredibly resilient. If we give it what it needs- whether slowly over time, or immediately increasing our intake, we see positive adaptations take place as the body regains a balance from the inside-out. 

To put it simply, you cannot gain weight from eating too little. However, routinely eating too little or cutting calories for too long can put you at a greater risk for your body needing to compromise the necessary functions that help you maintain and/or pursue a healthy weight. Making sure you focus on getting adequate nutrients should always come before trying to hit caloric goals for things like fat loss. If you can make sure your body has what it needs, hitting your goals will not only be easier, but your body will thank you by feeling, performing, and looking better along the way. 

References:

Joosen AM, Westerterp KR. Energy expenditure during overfeeding. Nutr Metab (Lond). 2006 Jul 12;3:25. doi: 10.1186/1743-7075-3-25. PMID: 16836744; PMCID: PMC1543621.