Survival Mode Isn't a Thing
… but your body does change when you lose weight.
Chances are you’ve probably heard someone complain, or had your PT tell you that the reason you’re not losing weight is because you’re in “survival mode”, or that your metabolism is broken / damaged — you’ve been dieting / calorically restricted for some time and now your body is going to hold on to every morsel of food that enters your system in order to survive.
This kinda happens, but it’s not survival mode. It’s metabolic adaptation. And it’s not that you’ll never be able to lose weight again, you’ve just got to be smart about it.
Way back when our ancestors had to hunt for their meals, food availability was unpredictable. Some times they caught dinner; some times they did not. Therefore, storing body fat was favourable, as it provided an energy source in times of famine, when dinner wasn’t being served up very regularly.
We don’t really need this in a first world food environment. We can access food pretty effortlessly [unless Karen has been panic buying] from the supermarket / our pantries whenever we damn well want — but try telling that to evolution.
But now, the human body has adapted mechanisms to prompt the storage of body fat, you know, just in case. This means now that dieting [or more specifically, prolonged caloric restriction] results in metabolic adaptations that aim to decrease your energy expenditure, increase your energy intake and increase metabolic efficiency. How this shows up? We feel tired [so we move less] and hungry [so we eat more], which results in us moving closer to caloric maintenance to prevent the depletion of our energy stores [aka prevent burning more fat that you so badly want to burn].
In a very small and concise nutshell,
An effective diet reduces your calorie intake
The human body “does it’s thang” and responds to this by kicking certain mechanisms in to gear
As a result, you feel more lethargic, causing you to be less active
And, you feel more hungry more consistently, causing you to eat more
Now, you’ve decreased your energy output and increased your energy input
You are no longer in a calorie deficit
You’re not losing weight
You complain that your metabolism is broken
Your metabolism isn’t broken and you’re not in survival mode. Your body has just adapted to the lower energy intake in an effort to keep your vital organs functioning — which is much more important to the part of your brain that you don’t consciously control — than whether or not you have a thigh gap. Your body and your metabolism is working exactly as it should.
So when the body “does it’s thang,” what exactly is it doing?
Systems to decrease energy expenditure.
Adaptive thermogenesis: as you lose weight, your body will urge you towards decreasing energy expenditure by making you less physically active — you’ll generally feel more lethargic and move around a lot less. So, your NEAT [which as I mentioned in my last article, can comprise up to 15% of your total daily energy expenditure] plummets as you fidget less, take the escalator, and ask your other half to make your coffee for you. This is the biggest contributor to decreasing your energy expenditure.
Thyroid hormone stimulates a bunch of processes in the body that require energy to occur. In the absence of thyroid hormone, these processes don’t occur, or occur less or more slowly and therefore, no or less energy [calories] are used in said processes. As we lose weight, thyroid hormone decreases.
Leptin is a hormone involved in stimulating energy expenditure. More leptin = more energy expended. Leptin is produced by our fat cells. Therefore, when we lose body fat, leptin in the body decreases.
Cortisol inhibits the activity of leptin. So leptin is already reduced when we are calorically restricted, then cortisol f*cks with what leptin we do have, leaving us moving even less. Cortisol also stimulates protein breakdown, which puts our muscle mass at risk. Our muscle mass is metabolically active, so less muscle mass = less energy output. You know what I’m going to say here — cortisol increases when we diet.
Systems to increase energy intake.
Leptin’s primary role however, is in appetite regulation. More leptin = we feel more full. So again, as we lose weight [and therefore, have fewer fat cells], leptin in the body decreases, leaving us feeling less full [aka more hungry] to drive us to seek out food.
The hormone, ghrelin stimulates appetite to make us more hungry. When calorie intake is restricted, ghrelin increases to drive us to consume more food.
Cortisol as we said, inhibits the activity of leptin. Since leptin promotes the experience of fullness, by inhibiting leptin, cortisol forces us to feel less full and more hungry.
Systems to increase metabolic efficiency.
When we metabolise the food we eat, our body converts the food in to a form of energy that is useable by the body. This conversion isn’t 100% efficient. However, when we have had our energy restricted [by means of a caloric deficit], this conversion process becomes more efficient. Therefore, we obtain more energy from the food we eat [increased energy in] and we give off less heat as a byproduct of the inefficiency of the process [decreased energy out].
So why is this actually worth knowing?
This might all just seems like a whole lot of physiology jargon that has little actual impact on you. But,
This explains why it gets harder to lose fat over time, and why it’s easier to lose the first five kilos than the last five. These adaptive responses are more profound as we edge towards lower body fat levels.
This explains why it can be harder to lose weight a second time. Perhaps you’ve lost weight before and it was really easy. You put the weight back on and getting it off now seems like mission impossible.
This explains why two people of same sex, height, weight and activity level may have profound differences in their TDEE. Perhaps your best friend can seemingly eat whatever they want. You’ve fought tooth and nail to get to the body weight you are now, but now you just smell a cupcake and gain 5kg. The person who has had to diet to get to that lower body weight [you] will burn fewer calories than the person who has always maintained that weight [your friend], because the latter hasn’t experienced these adaptations.
This explains some of why people “rebound” post diet, and why maintaining our new physiques is so damn hard. You can’t just go back to what you were eating pre-diet now that you’ve achieved your goal weight. Your body has adapted and you will likely need to maintain a lower caloric intake in order to maintain this new lower body weight.
I understand this all sounds pretty grim, but this is evolution and it’s designed to support the continuation of the human race. So I mean, try to fight with that. However, there are certainly ways we can reduce the effects of metabolic adaptation so we can push towards and maintain the physique that we want.
So, if you feel like some of this might be applicable to you — perhaps you have lost weight before and now it won’t budge — there is no need to throw your hands up in the air just yet. In my next article, I discuss some of the strategies we can implement to reduce the extent to which we experience metabolic adaptation, so that we can be rewarded for our weight loss efforts. You can read it here. I think it will give you peace of mind :D
Billie x