Once you start talking about losing body fat, there are a bunch of people come up with this idea of starvation mode! I understand where this comes from and we definitely need to answer the question, ‘is this real or not?’
To sum up, it isn’t real.
The starvation mode effect, is the idea that as you start to lose weight the body goes into survival mode and starts storing body fat, or becomes primed to store body fat later on.
However, what does happen, when we lose body fat is that our metabolic rate does in fact, slow down. There are a couple of reasons for this. I’ve talked about the metabolism in other podcasts and in other blogs, so do go ahead and check those out.
There are four parts to the metabolism, there is the base metabolic rate, the digestion of food that causes energy burn. There is the exercise expenditure and the non exercise expenditure.
As we lose body fat, our metabolism goes down in several ways. Our metabolic rate does slow down slightly, the base metabolic rate. We also burn less energy because we’re eating less food. We get more efficient at exercise and that expenditure goes down. Also, our bodies conserve more energy by moving less outside of formal exercise.
All these things have a big effect on the metabolic rate as a whole as we lose body fat. This is natural, because the body is doing these adaptations to stop us losing from body fat.
While not being the ‘starvation mode’ that is often bandied about, it is a case of it being an adaptation to slight starvation. Our body is conserving energy because it is getting less food.
Your metabolism though, does not completely grind to a halt, it adapts. We also get adaptations to our hunger and appetite hormones the longer we spend in a calorie deficit.
Unfortunately we get hungrier, and we get less satisfied from the food that we do eat as well. This then does make us more prone to overeat. The further into a weight loss phase that we go and especially after the weight loss phase is over.
It is not that your body is primed to necessarily store body fat when you eat more food again, or hold on to it. But, because of the adaptations of the lowered metabolic rate and the increased desire to eat food. It is easy to then get ourselves stuck, when we’ve reached the end of a weight loss phase. We either go back to prior eating behaviours, or we just stuff our face with excess calories because we’ve gotten bored of the diet.
With regards to putting this starvation mode myth to bed; There was a guy who performed a 382 days supervised fast, where he lost 125 kilos at a rate of 0.33 kilos per day.
The rate of his weight loss did slow down, as he went through it, because as he started to lose more and more weight his metabolic rate would have slowed down because he was a lighter human being! As well as because of what I mentioned above.
With weight loss, the metabolism adapts maybe 15 to 20% lower after a hard diet and only happens at around 10 to 20% weight loss. There is no evidence to suggest that it continues to happen after that initial phase.
The beauty of what happened in this experiment is that he lost all of this weight and after the fast he was able to maintain all of the weight that he lost. Five years later when they followed up with him, he was still within three to five kilos of his body weight after the fast.
His body didn’t just put all of the body fat back on after his fast because he was able to change his behaviours and hold on to the weight loss over the long term.
Similarly, in the Minnesota starvation study, they starved a group of men because they wanted to see how to refeed people after being prisoners of war. All of the men continued to lose weight throughout the study on super, super, super low calorie diets’ Their metabolisms did slow down, their exercise expenditure and their non exercise expenditure went down, but they continued to lose weight, despite being starved.
Their bodies didn’t hold on to the body fat that they had. The answer then to all of this is that starvation mode isn’t real.
What can happen is that your metabolic rate and all of the other things I’ve mentioned can be adjusted through a weight loss phase. This can be enough over time to turn a calorie deficit into calorie maintenance.
Then the issue becomes, what do you do when you’ve hit a plateau?
To answer that question, we’re going to be talking tomorrow about whether or not you need a diet break. If you’ve been chronically dieting for a long time, the answer is probably yes. So please check back for tomorrow’s blog.