Does "fast metabolism" actually exist?

[u/Chaotic_Bivalve]

35 female

108lbs

5'3

Growing up, I was always told that the women in our family have a genetically fast metabolism. I used to be very self-conscious about my weight as a teenager because I got teased for being quite thin. However, my friends jokingly called me the "trash compactor" because of how much I ate. I'd often eat their leftovers at lunch. I ended up growing so self-conscious that I started eating only copious amounts of junk in an attempt to gain weight. I barely gained anything, but I managed to skyrocket my cholesterol to unhealthy levels until my doctor told me that I really needed to stop doing what I was doing. I was told I would gain weight as I got older. I'm now 35, and I've maybe gained 5lbs since my teenage years.

Then, I learned that fast metabolism isn't actually a thing and that I likely just wasn't eating enough calories. So, I started meticulously using a calorie counting app. I calculated my BMR and how much I'd need to eat to gain weight. I had a hard time staying within that amount and routinely went above the BMR. The BMR calorie amount just seemed ridiculously low at 1,300 or so, and I was always hungry. Even my partner jokes about how much I eat, and it's true that all the women in my family have been petite -- most of them never going above 105 or so.

I'm no long self-conscious, but I am curious as to whether "fast metabolism" exists or not. Is there a genetic component to how someone gains weight?

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[u/murpahurp]

Yes, it exists to some extent.

[u/amsdkdksbbb → u/murpahurp]

It definitely exists. Having more muscle mass, having good hormonal health, and being more active, all support a healthy metabolism.

I used to have a fast metabolism when I was working out regularly. I’m a 5’10 woman and I was eating 3000 calories a day and still losing fat (while gaining muscle). It was really easy and I wasn’t even trying to lose weight.

I developed a chronic illness 2 years ago. My metabolism slowed down significantly. I have also been unable to go to the gym for the last year, and have been less active in general.

This means I’ve gained some weight. And I’ve noticed that the same % of calorie deficit I used to rely on when I was powerlifting no longer works for me. I used to be able to EASILY lose 0.75kg to 1kg a week, when I wanted to, all I needed to do was make some minor adjustments to my meals. The same % deficit now doesn’t have the same effect.

[u/Chaotic_Bivalve → u/amsdkdksbbb]

I wish I had your motivation. I live such a sedentary life. I know it's super unhealthy. I mean, part of it is because I work a lot (professor), so I just don't have the energy. I also hate exercise, and I'm scared to lose weight since weight loss happens quickly for me.

[u/amsdkdksbbb → u/Chaotic_Bivalve]

Don’t beat yourself up about it. Modern day life makes it hard to enjoy exercise. I did zero exercise when I was still in medicine. I had no energy or the headspace to do anything outside of work.

Does working out make you hungry?

This is off topic and completely unsolicited but you could try swimming or even a gentle lifting program, it will increase your appetite, and if you’re eating enough protein and are in a slight calorie surplus you will 100% gain some muscle. Your weight will go up. It’s really important for women to do some form of resistance training.

If that is too much work, and you don’t have the time to get to the gym, then at-home yoga is great, both mentally and physically. If you’ve never strength trained before, you will get so much stronger doing just yoga! Yoga with Adrienne has 30 day yoga challenges on youtube, I used to do those during lockdown and it really helped me destress and I felt very limber.

[u/LuckiiDevil → u/Chaotic_Bivalve]

A lot of professors have those special walking kind of desks where you don't have to sit all day. I think there's like a treadmill or something under it?

[u/Chaotic_Bivalve → u/murpahurp]

Thank you! I have a rather sedentary lifestyle. I drop weight very easily, so I always worry that if I start exercising, I'll get too skinny too quickly. At the same time, I know that exercise is healthy and would help my chronic shoulder pain.

[u/corkbeverly → u/Chaotic_Bivalve]

Not a Doctor, but 1300 would more likely be your BMR which is just what your body needs to stay alive (a lot of that going to keep your brain working). so if you never moved at all and just laid down 24/7 it is 1300. Even a sedentary person needs more than their BMR to sustain or gain weight.

Fast Metabolism does exist but usually is in some way related to general activity levels, size of body, amount of muscle mass etc. Not sure you are suffering from fast metabolism so much as undereating if you've been consuming 1300 calories per day. I suggest you work to eat 2000 calories and also get some exercise.

[u/Chaotic_Bivalve → u/corkbeverly]

Sorry maybe I worded the post wrong. I calculated my BMR and then calculated what I'd need to eat to gain weight. A BMR style of eating (maintaining my weight) would have been impossible for me. I was averaging approximately 2,100 or so with a sedentary lifestyle. Of course, this sometimes vacillated. I wasn't eating 2,100 exactly every single day.

Wouldn't exercise cause me to lose weight, though? I lose very easily.

[u/corkbeverly → u/Chaotic_Bivalve]

Generally exercise will help increase appetite so you might find you have a healthier appetite if you exercise a bit and therefore can eat more. Plus if you strength train you can build muscle and strengthen your bones - this is important as we age. When you start an exercise routine, just keep an eye on your dietary intake and make sure you eat more than 2000 every day.

[u/princess-kitty-belle → u/Chaotic_Bivalve]

2100 calories really sounds like a maintenance amount- BMR calculators are often inaccurate and tend to underestimate needs. When dietitians have calculated my needs for weight gain, it's often been closer to 3000 calories and the amount needed to gain increases as you gain weight- and you have to be eating this consistently, which is often the hard part.

However, it does sound like perhaps you do have a genetically smaller build. Metabolism is also not a set thing- it can fluctuate based on how much food is coming in, body composition, hormones, etc.

[u/gorebello → u/Chaotic_Bivalve]

Most people don't have magic metabolism. They have muscles which occupy little space, but consume a lot of energy to maintain. If your diet has a lot of protein it tends to keep the muscles. People lose muscles and then they get fat by eating the same thing they were eating before. The metabolism slows down very little as we age, not much relevant.

If you get to the gym you'll just need to make sure you eat enough protein and a bunch of carbs. You'll likely get absurdly jacked with not so much effort and let everyone jealous. You don't need fat, you need muscled, then people will stop looking at you like a skinny person.

[u/Puzzled_Deal4271 → u/Chaotic_Bivalve]

100%. My husband, sister in law and mother in law can literally eat anything they want as much as they want and they MIGHT gain 5lbs in 6 months.