You’re not in starvation mode. The theory of starvation mode goes something like this: “if you don’t eat enough calories, your body thinks that it’s starving and will shut down your metabolism. So maybe that’s why you’re not losing weight. “ This sounds catastrophic and sciencey, but it’s not happening to you.
Experiments have been done on this- we can look back to the Minnesota starvation experiment conducted on volunteers during World War 2. Researchers starved young men for 6 months to help determine how best to treat victims of mass starvation from the war in Europe. They didn’t look like frustrated folks who can’t seem to lose the last 10 pounds: they looked like they were actually starving.
During the study, men were suddenly given only 50% of their calories and expected to burn in excess of 1000 calories more than they consumed each day.
So what gives? Why is it that sometimes we feel like we’re eating so little that we surely must be at a big deficit, yet our weight loss stalls? It turns out that there are reasons that we might not be losing weight optimally, but it’s not because we’re starving.
Hungry people eat.
The men in the experiment exhibited behaviors that show how people will go to great lengths to get food when they’re hungry. Even though they were volunteers, the men would occasionally eat food not on plan. They were apathetic, exhausted, and mentally not well by the end of the study. 1
Imagine having that primal urge to eat when food is plentiful. Despite trying to restrict calories, we usually find ways to take in extra nutrition, even without thinking about it. As I talked about in my article about the pitfalls of calorie tracking, people aren’t very accurate about estimating how many calories they consume.
Another behavior is binging – when you starve yourself, you will get to a point where you fantasize about food all the time. At some point, a binge will happen. We don’t always factor in the binges. Nobody wants to remember those.
Changes to our Metabolism
So things don’t come to a grinding halt when we reduce calories. The men in the experiment continued to lose significant amounts of weight until they reached around 5% body fat. That’s extremely low, for what it’s worth.
Another study featured a medically-supervised obese man who fasted for 382 days. He continued to lose weight throughout the study period, though his metabolic rate did slow down. 2
How our Metabolism Slows
When we lose weight we don’t have as much body tissue. Our tissues require energy in order to exist – once we have less tissue, the amount of energy we expend decreases too. 3
This accounts for some slowing of our metabolic rate. Some also think that when we eat more food, our NEAT goes up. NEAT stands for non-exercise activity thermogenesis. This is science-talk for “stuff you do during the day that burns calories outside of exercise”. Some people have a big NEAT, others not so much. Ever see someone who seemed to fidget all the time? That’s NEAT. Washing the dishes, picking up clutter, watering the garden — this is all NEAT.
If we have less fuel in our bodies, we might be less inclined to feel energetic and as a result, may have a decreased NEAT. That results in fewer calories burned each day. With that said, if we’re operating at a very low calorie count, we probably aren’t busting our butts at the gym too. If we don’t work as much or as hard in our workouts because we’re hungry and tired, that results in a lower TEE (thermal effect of exercise).
We also experience a decrease in TEF, or the thermic effect of food when we eat less food. It takes energy to digest what we eat. This accounts for around 10% of our daily intake.
Eating at a big deficit can be stressful. When we eat very few calories, our body produces cortisol as a stress response. Increased cortisol causes us to retain water. Guess what that means? A bigger weight on the scale. When we eat more calories, sometimes we experience the “whoosh” effect, as nutrition expert Lyle McDonald calls it. 4
Adaptive Effect of Weight Loss
The adaptive effect of weight loss describes how our metabolic rate slows more than we would think based on the amount of total weight lost. Hormones are at play here – our amount of leptin and thyroid levels change.
What it all Means
First of all, if you feel like you’re in “starvation mode” you’re most likely eating more than you think you are. It isn’t a fun reality, but overwhelming evidence points this out.
Second, the effects of a metabolic slowdown are there, though I haven’t seen evidence to support it being significant. Research results seem to vary in how much of an impact hormonal changes make.
We also don’t always account for the normal fluctuations that happen in weight – from day to day, we have different scale weights. Some days we hold a lot of water. Or we’re full of poop. Women have bigger swings in scale weight with these factors too due to our menstrual cycle.
What to Do Next
- Eat the food, but not too much. It takes time and tinkering to figure out how much we need to create a deficit. Meet with a qualified nutrition coach or registered dietitian if you are having a hard time figuring out specifics.
- Keep your calorie deficit moderate – there are indications that deeper deficits (>500kcal) have a bigger impact on metabolic slowdown.
- Some people find it helpful to take “diet breaks” when they’ve been stuck and are certain that they are eating at a low calorie range. This can decrease the amount of cortisol we produce, both from the physiological effect of eating at a deficit and then mental relief from restricting calories.
- Lift weights. Eat protein (“brotein”). Both help preserve muscle mass, which in turn increases energy expenditure. However, it isn’t by as much as you’d think. You won’t magically turn into a fat blaster. However, you might gain some sweet looking biceps to flex. Rawr.
- Realize that calories in/calories out matters most, but how we make that happen can be frustrating and a bit of an experiment with our bodies. Ease in and have patience.
The Minnesota Starvation Experiment is fascinating – if you want to read more about it, check out these links:
Thanks for reading!
- Ball, J. (2014, January 20). The Minnesota starvation experiment – BBC News. Retrieved September 1, 2015. ↩
- Stewart, W., & Fleming, L. (1973). Features of a successful therapeutic fast of 382 days’ duration. Postgraduate Medical Journal, 203-209. ↩
- Schwartz, A., & Doucet, É. (2009). Relative changes in resting energy expenditure during weight loss: A systematic review. Obesity Reviews,531-547. ↩
- McDonald, L. (n.d.). Of Whooshes and Squishy Fat. Retrieved September 1, 2015, from http://www.bodyrecomposition.com/fat-loss/of-whooshes-and-squishy-fat.html/ ↩