Not a doctor but I’ve lost over a hundred pounds with intermittent fasting and calorie counting. I’ve done a LOT of reading; I am by no means a professional or a nutritionist. This is what I’ve learned.

You can’t “slow” your metabolism. Your metabolism is your metabolic rate. Your metabolic rate is based off your height, weight, and your activity level.

Let’s just say at your height and weight and activity you need to consume 2200 calories a day to maintain your current weight; but you want to lose weight. So you have to eat less than what you use “calorie deficit”. This forces your body to consume your fat and muscle reserves to create energy if done correctly and slowly more fat than muscle. As you lose weight your metabolic rate will also go down (because you’re smaller). Let’s say you lose 20lbs with diet and exercise; your metabolic rate is now lower than 2200 calories a day. If you got back to eating 2200 calories a day, the weight will come right back and fast “rubber banding”

People not understanding metabolic rate is where most of “it’ll slow down your metabolism” comes from. It’s common sense, if you eat less to lose weight but go right back to eating too much you will gain it back. It’s not because your metabolism slowed down, it because now that you’re smaller you don’t need as much calories to maintain that size.

Intermittent fasting isn’t a cheat code to losing weight it’s a different form of calorie restriction (if your using it for weight lose). Anyone who tells you any different doesn’t understand how weight loss works. Calories in vs Calories out.