I apologize if this has been asked and answered here before but I’m curious. I’ve read that not eating enough calories can severely deplete your metabolism, yet people do 72 hour or more fasts and it supposedly boosts their metabolism? Does a 16-8 IF boost your metabolism?
Very curious to understand how it works.
Different hormones get activated when you are in the fasted state. Adrenaline, growth hormone etc go up, and actually increase metabolism. Your body is feeding itself as many calories as necessary of it’s own fat, not slowing down to compensate for constantly being in the fed state on too few calories.
If you’re eating at a caloric deficit you’re going to lose fat, there’s no way around. A fasted state means that you’re in a state where insulin levels are low and thus you’re able to metabolize your fat instead of your glycogen stores. If you are constantly eating your insulin levels remain elevated and you’ll less likely burn fat as your main source of energy, rather glycogen/glucose
Dr Jason Fung explains the science here. https://youtu.be/BeC_gIR2Z14
I recommend his YouTube videos. They are very informative and have been instrumental in helping me lose 27kg
Also his book The Obesity Code is excellent. Borrow it from your local library.
Most of these things are more a function of doing them for extended periods of time, ie more than a few days. It’s about a pattern of behavior. For instance, not eating 1,200 calories minimum one day isn’t going to cause you to keel over dead, but do it for weeks and weeks and you’ll potentially suffer from malnutrition issues as it becomes hard to get the body everything it needs on so little.
As for the metabolic boosts of IF, it’s marginal. Like a couple percentages at most in some studies if no difference at all.
The one aspect that IF does potentially help to address is metabolic adaptations. If you’re eating at a deficit but still have high insulin, from what you eat or how often, the body won’t break down fat while insulin is high. IF creates more time for digestion to die down and for the deficit to properly get directed to fat stores.
The whole metabolism destruction thing is big scare in a similar way how they tell you if you do IF you will feel lethargic. Must eat every few hours blah blah.
I’ve been in 700cal weekly deficit for almost a year many days more than that…and guess what, my metabolism is exactly where it should be. And I did RMR test so know accurately all thed data. In fact I burn 100cals more and doctor attributed it to my 4 day per week weight lifting sessions.
If you diet properly and don’t do massive amounts of cardio like most people start to do when they begin a diet… nothing will happen to your metabolism. Weight lifting is helping a lot keeping the engine burning and really our bodies are not that easy to mess up.
I don’t know what exactly you’re asking but one thing I’m sure of is that starvation mode is not real and that has been proven, so no, not eating enough calories doesn’t destroy your metabolism, not eating enough calories only burns more fat.
Your body doesnt work like a combustion engine.
Its not as simple as calories in, calories out.
You dont “burn calories”. You metabolize food for energy, and you use it to construct your body.
Fat storage is cause by your hormones.
Your hormones behave differently when you are eating calorie restriced meals regularly, than they do when you fast intermittently.
So you achieve a different result from having a caloric deficit. Weight loss.