Can eating too few calories cause weight loss to stop? Well, yes and no. Like many things in the health and fitness world, it’s a bit more complicated than the magazine headlines and Instagram captions would like us to believe. I’m sure many of you have heard the phrase starvation mode. The idea is that if you eat too little your metabolism will slow down and you will actually gain weight. Technically, this isn’t possible as our bodies are subject to the laws of thermodynamics. (Energy can neither be created or destroyed) If it were the case people wouldn’t be starving and dying from malnourishment in third world countries. So what is going on? I will do my best to briefly explain at a high level what’s happening and why eating too few calories is not the answer to fat loss.
Okay, let’s cover some basics. In order to lose weight you must expend more calories than you consume. It’s really pretty simple, but let me show you the factors that determine how many calories you burn in a given day.
BMR – Base Metabolic Rate: the energy your body needs to stay alive
NEAT – Non-Exercise Activity Thermogenesis: the energy you burn through activity but not deliberate exercise, e.g. walking around your house, playing video games, shopping
EAT – Exercise Activity Thermogenesis: the energy you burn through deliberate exercise e.g. Weight training, running, swimming, playing basketball
TEF – Thermic Effect of Food: the energy required to digest, absorb and store the food you eat
These factors combine to give you your TDEE or your total daily energy expenditure.
Now, let’s clear something up. Many people want to lose weight, but nearly everyone wants that weight to be fat loss, not muscle. This is a really important distinction because it is very possible to lose weight and still not be achieving the look you’re after because the weight you’re losing is muscle. This is where very low calorie diets can be detrimental. This is a double edged sword because every kg of muscle requires roughly 45 cals a day whereas fat requires only 30. When you lose muscle mass you are losing the ability to burn more calories. The same thing is true of fat, but to a lesser degree. The more muscle a person has, the more energy they expend at rest. So, if you’re eating a super low calorie diet you risk losing muscle. As you lose weight your body requires fewer calories to operate. Therefore, what may have been a moderate caloric deficit at 200lbs is no longer a deficit at 175lbs. At this point, to sustain weight loss you’ll need to reduce calories or increase exercise. However, if calories are too low you will not have sufficient energy to increase exercise and recover properly leading to overtraining or injury. Those who continue eating far too few calories for a prolonged period of time also risk creating hormonal problems that further complicate the process.
Unfortunately, people want quick fixes so they start a diet with massive deficits only to create health problems and later abandon the process altogether. I should also note when people employ this kind of strategy only to give up they end up adding all their lost weight and more back.
The best way forward to meet your goals is to find someone who can help you understand your current state, look at your lifestyle and create a sustainable nutrition plan to get you started. Proper nutrition combined with resistance training over time will yield incredible results. The cool thing is it’s not a gamble. It’s completely controllable. If you stick to the plan and do the work you will get the results. No talent is needed, only commitment.