[Hermitian909]

I think you misunderstand the failure mode. How do you measure calories out? Is that number static? How does it change over time?

My father is obese, and has been for many years. At the weight he usually hovers at, his BMR appears to be ~2,500 calories. He can lose weight from here no problem eating ~1600 calories a day, not easy, but not to hard.

The problem is, that after about 15 lbs of weightloss, he plateaus. Dexafit scans confirm there's been a massive reduction in BMR. By the time he's dropped 20 lbs his calorie counts generally need to be in the 1200s to lose weight, which is just torturous. The longest he ever last at these really low calorie counts was probably a year, I'm significantly smaller fitter than he is and I could not have lived a productive life on the diet he was eating.

I'm not sure how common this kind of response is, but his doctor's didn't seem to think it uncommon.

[JackMorgan]

I've seen this play out on myself. I finally realized that I can only lose about 10lb of fat before my body refuses to lose more. Further extreme calorie cuts will only cut muscle. Including dropping to zero calories on a extended fasts. One year I got down to medically underweight (and could wrap my whole hand around my upper arm) and I still had a belly so big I couldn't see my toes when standing. I apparently have some extremely famine resistant genes.

I eventually lost (and kept off for the last 6 years) all the weight I wanted by cycles of cutting and bulking. I'd slowly raise my calories, eventually settling at a slight 10% surplus for eight weeks. I'd then start tapering calories for eight weeks, eventually losing about 8 pounds of fat. I'd repeat the cycle, gaining about a quarter pound of muscle and 2 pounds of fat. Then repeat again.

Obviously this is a huge hassle, but I was able to go from obese to the lower end of healthy weight, and in the meantime got my deadlift to 2x my body weight.

Also so many veggies. Lunch and dinner, 2 cups of veggies before the main protein.

Now to keep it off, I still eat the veggies, and I also drink a ton of water before a meal. And lastly, our meals are pretty much just variations of lentils, legumes, and chickpeas. Those have good protein and fiber. We'll add olive oil for fat. Some pita, high fiber tortillas, or whole wheat bread adds carbs.

[willcipriano]

> At the weight he usually hovers at, his BMR appears to be ~2,500 calories. He can lose weight from here no problem eating ~1600 calories a day, not easy, but not to hard.

So he is something like 60, sedentary, 5 foot 10 and 280 pounds. That results in a estimated TDEE (BMR plus accounting for calorie burn of basic life activities) of 2504 calories per day.[0]

> By the time he's dropped 20 lbs his calorie counts generally need to be in the 1200s to lose weight

In this scenario that would drop his TDEE to 2395 calories per day.

At 1200 calories a day, if those numbers are correct should see at least 2 pounds a week of weight loss. If he is maintaining, check your priors.

He is either overcounting exercise, over estimating TDEE or under counting what he eats. If you have weights and accurate calorie counts you can extrapolate his TDEE from that and know exactly what deficit to eat at.

[0]https://tdeecalculator.net/

[Hermitian909]

> In this scenario that would drop his TDEE to 2395 calories per day.

This is what naive calculations say, this is not what a DEXA scan says. His body is actively reducing calorie expendature well below what you would expect.

I have tried taking over his calorie counting for a week to help him, as someone who manages my own weight successfully I don't think I would overcount by a factor of 2. The chance he ate calories I was unaware of during that week is approximately zero (highly controlled environment, never left apartment)

[willcipriano]

He needs to go into a whole body calorimeter[0] to prove it if what you say is true. It will be a world first.

[0]https://www.uhcw.nhs.uk/leading-research/about-us/our-facili...

[Schiendelman]

It also doesn’t sound like he has to drop to 1200 cals to lose weight! More like 1500-1700.