Help me with the maths

How do you know how much she's eating?

Her TDEE is likely less than 2000-2300.

Orphia wrote: »

A friend has lost 22 lbs in six weeks.

She started at 220 lbs.

What's her average daily calorie intake?

She might do a half hour walk a day but is otherwise sedentary.

I think she's fairly short (5'4"?) and in her fifties.

Just wondering if she's dangerously undereating.

The problem as I see it is that even many professionals don't agree on healthy weigh loss intake. I'd say those that lean towards safe usually state 1% of body weight per week or maybe even less.

But to be honest, I think that it could be safe to have a specific diet that was very low calorie, as long as the professionals made sure to account for nutrition specifics. I person of that height and weight is probably well into the upper 30s or maybe even 40% body fat. Even at her current weight that means her body can utilize fat to get through most of the day based on average TDEE for someone who isn't doing much exercise.


But based on your question she was at a deficit average of about 1,800 calories per day.

Helping you with the maths, but we'll have to make some assumptions to account for things we don't know:

22 lbs in six weeks is a bit over 3 1/2 pounds a week, which works out to a daily deficit of about 1830 calories, although it's probably less than that because some of that weight loss is almost certainly water (unless six weeks ago wasn't the beginning of her weight loss, but I assume you would have mentioned it if it wasn't). So let's assume about 4.5 pounds of water loss from using up her glycogen stores and 17.5 pounds of body mass lost, mostly fat, for a weekly loss of just under three pounds of body mass, and a daily calorie deficit of roughly 1450 calories.

At 220 lbs, 5'4", in her 50s, little exercise, no resistance training, I would guess she has more than 30% BF, but let's be conservative and assume she's somehow as low as 25% BF, or 55 lbs of fat. Humans can recover roughly 30 calories per pound of body fat per day. 30 X 55 = 1650.

So, conservatively (remember, we're only crediting her with 25% BF in this exercise, which is pretty low for her stats), she can generate more than 1600 calories from her fat stores each day (at least at the start; it will diminish as she loses fat), and she's likely averaging a daily calorie deficit of a little less than 1500. I wouldn't call that dangerously undereating on the face of it from a deficit standpoint.

It's cutting the deficit closer to the theoretical maximum supportable by her fat stores under these assumptions than I would care to if it were me, because I favor a muscle-sparing approach to weight loss, but remember that she's likely got a good bit more than 25% BF (just based on her stats and the activity level you state for her, 35% or 40% wouldn't be unreasonable, in which case she's probably nowhere near the calorie deficit she can support from fat stores, even if none of the 22 lbs was water weight).

However, it's hard to imagine her TDEE is above the low to mid 2000s, even if your perception of "sedentary" doesn't account for walking around on the job or around the house cleaning, minding children, etc. The conservative daily calorie deficit of 1450 calories calculated above (the one that assumes 4.5 lbs of water weight lost) would put her intake around 1000 calories a day even with a TDEE in the mid 2000s, and even substantially below 1000 calories if her activity level is truly sedentary (say, a TDEE of 1800 calories, which would indicate a daily intake below 500 calories). That's not something she should be doing without a doctor's supervision. And there are nutrients that she needs that she can't generate from her fat stores (protein, essential fatty acids, vitamins, and minerals, and some fiber wouldn't hurt), and I would wonder with that large a deficit if she's enough of those nutrients.

A lot of people drop a large amount of water weight right off the bat. She could have lost like 10 lbs the first week and then tapered off to a more reasonable amount or some people don't give a damn about being healthy and just want to be skinny at any cost. Hard to say which category she might fit into without more facts.