I’ve realized that I don’t feel healthy anymore due to weight gain. Nothing too bad, but I don’t want it to become bad.
Several factors influence your weight drastically which we don’t mean when we talk about “losing weight”. For example, losing a limb or losing blood due to an accident. A bit less obvious is water or food in the stomach. Yes, it influences your weight a lot in a short time if you donate blood or if you drink 3 liters.
No, we mean body fat. The only way to lose it is a calorie deficit. Meaning your body needs to use more energy than it gets through food.
Burning Calories
The energy used by your body depends on many factors:
- Age and size: Growing children need a lot of energy for their size, but bigger bodies need more energy overall: a 25-year-old man needs about 2400 calories whereas a 6-year-old boy needs about 1400 calories.
- Gender: A woman between 31 and 50 who isn’t active needs about 1800 calories a day, a man between 2200 and 2400.
- Activity: Doing sports needs energy. A very active 18-year-old man needs about 3200 calories whereas an inactive one needs about 2200 calories.
Let’s calculate
The most extreme calorie deficit is when you don’t take any calories. How much would that be per day?
Assuming that your body would only burn fat (which it doesn’t):
- 3500 calories in one pound (lb) of body fat (source). That is about 7716 calories per kg of body fat.
- Assuming the body needs about 2000 calories per day.
That would mean extreme fasting would result in a weight loss of about 260 g per day or about 1 kg every 4 days. In other words 7.8 kg per month.
If the person is a highly active man who needs 3000 calories per day, the numbers are:
- 388 g per day
- 1 kg every 2.6 days
- 11.6 kg every month
Those were the extremes. More likely is something like a 300 calorie deficit. That would be:
- 39 g per day
- 1 kg every 26 days
- 1.2 kg every month
Implications
Those numbers were important to me to set expectations right. They might also be important to others to know when advertisement, influencers, and blogs are lying or at least exaggerating.
The realistic numbers in the end show that losing weight is a long-term goal. It might take several years. It needs a better diet and more sport. Not fasting for a few days.