The “Calories in vs calories out” method isn't as simple as some enthusiasts think. Therefore, some people who reduce the number of meals hoping to lose weight or aiming the same goal start doing sports without adjusting their nutrition don't get the desired results.
Our body is much smarter. Sudden reduction of calories in causes a similar reduction in calories out, and no weight is lost as the body balances its energy budget.
The most famous Minnesota Starvation Experiment has shown exactly this.
- 36 healthy men
- first 3 months they received 3200 cal per day
- over the next 6 months - 1570cal
As a result, all body functions that require energy experienced an immediate across-the-board 30 to 40% reduction which wrought complete ruin:
- strength reduced 21%
- heart rate slowed from 55bpm to 35bpm
- body temperature dropped to an average of 35.4C
- blood pressure dropped
- men became exhausted and dizzy
- they lost hair, and their nails grew brittle
- psychologically they experienced a complete lack of interest in anything but food
The men should have lost 35.3kg, but the actual weight loss was only 6.8kg.
I love this analogy that Jason Fung made in his book "The Obesity Code": Imagine operating a coal-fired power plant. Every day to generate energy, we receive and burn 2000 tons of coal. Now all of a sudden, we receive only 1500 tons of coal a day. Should we continue to burn 2000 tons of coal daily? Then, the power plant would shut down. Massive blackouts develop over the entire city. So it'd be smarter to burn 1500 tons or even 1400 to be on the safe side, then a couple of lights will go dimmed, but we'll avoid massive blackouts. Massive blackouts in this analogy are the death of the body.
The bottom line. Regardless of if you are on a diet or not, it's good to know how your body would react if it doesn't get enough energy during a prolonged period. Pay attention to the signals the body makes to show you that something goes wrong. It's the best way to define what works and what doesn't work for you.
What do you usually feel when your energy is at zero?