Starvation Mode
What is it?
I receive more emails about the dreaded “starvation mode” than any other topic. For those who don’t know, depending on who you ask, the starvation mode is a metabolic crash in response to consuming too few calories. Go figure that this doesn’t apply to anorexics who continue to lose weight even when calories are much lower for extended periods of time.
Fat loss is not a linear process. Plateaus are not only possible… they’re probable. Therefore they should be expected. By the time I’m done with this section, I’m hoping that each time a plateau occurs, you’re not running around frantically trying to fix your ‘broken metabolism.’
If I were to ask a room full of people what their definition of the starvation mode is, I’m sure I’d receive a wide array of answers. The common ones would likely go something like this:
It is when your metabolism shuts down by eating less than 1,200 calories.
Or…
It is when your metabolism slows down so much in response to a calorie deficit that you can’t lose more weight or you actually gain weight.
In actuality, there is some truth to what people are calling the starvation mode. There’s also a whole lot of fiction and ignorance thrown into the mix as well.
Here’s the low down…
In the research, what many call the starvation mode is typically referred to as adaptive thermogenesis. I prefer the latter simply because it implies that it’s a process rather than an immediate response to dieting. It’s a messy term though so I’ll use starvation mode or starvation response throughout this section.
The starvation mode isn’t something that happens in the flick of a switch. It’s a continual adjustment your body undergoes in response to an energy shortfall. It’s your body’s way of conserving itself during times of famine. Thank your local caveman.
This adjustment leads to a reduction in energy expenditure. Remember, total energy expenditure is a combination of basal metabolic rate, energy expended through activity, and energy expended digesting food.
Its Impact On BMR
Research definitely points toward a reduction in BMR in response to a calorie deficit and fat loss. Here’s the thing though… when we lose weight, our energy expenditure is going to decrease with or without the starvation mode. A lower weight means less tissue to support, less mass to move around, etc.
The starvation mode comes into play when this drop in energy expenditure is greater than what would be predicted given the decrease in weight. It’s an overcompensation, if you will. This phenomenon is why someone who’s naturally 135 lbs will likely have a higher energy expenditure than someone who dieted down to 135 lbs from 200 lbs.
While the ‘buzz’ suggests there’s a specific calorie intake that triggers this reduction in BMR, there’s not a lot of truth to that. It’s really something that’s going to happen regardless of the size of the calorie intake or deficit. The driving factor seems to be fat mass. The more fat you lose, the greater the starvation response of BMR you’ll realize. Smaller deficits will merely decrease the rate at which you lose fat and thus slow down the metabolic adaptation. Both paths point to the same destination though.
Here’s the thing… the starvation mode does not completely shutdown your metabolism. If it did, you’d be dead! It merely drops your energy expenditure slightly. The largest recorded drop that I’m aware of was observed in Ancel Keys’ Minnesota Starvation Experiment.
This research placed relatively lean men on a 50% calorie deficit for 6 months. While there was a 40% drop in metabolic rate, roughly 2/3 of this was accounted for by the drop in body weight. In other words, the majority of the reduction in metabolic rate was expected given the smaller bodies.
That’s a 15% drop in metabolic rate due to the starvation response in lean men dieting for 6 straight months on 50% of their calorie needs. Their average ending body fat percentage was something around 5%.
Hardly anyone reading this is in this situation. Most of you likely have excess fat to lose and you’re not going to be eating such low calories for extended periods of time. When you have an abundance of fat and you’re not starving yourself, the starvation response is going to play a much smaller role in dropping BMR.
Keep in mind that this isn’t happening meal to meal or even week to week. This is a longer term phenomenon. In fact, some research suggests that metabolism increases with a day or two worth of fasting.
None of this implies that a calorie deficit will no longer work. Rather, this information implies that after you’ve lost a considerable amount of fat, your predicted maintenance might be inflated.
