how quickly can a severely obese person safely lose weight?

I’m not looking for medical advice and all replies are accepted as non-expert and non-binding.

Say you start with a person weighing in excess of 250Kg and nearly bedridden. He checks into a hospital under a doctor’s care, is put on a very restrictive diet and given physical therapy at least daily. He begins losing weight and as his health and mobility level improve he begins doing more and more therapy and exercise. If needed, his diet become slightly less restrictive as his activity level goes up but he’s still given the minimum number of calories he needs each day and far less than he used to consume.

Under these conditions, what’s a realistic six month weight loss goal?

Logic tells me that the weight loss would be a constant number of grams of fat each day, regardless of the total weight at the start of a constant regimen. If the guy weighs 250 kg when he starts, a certain regimen will result in losing the same number of grams of fat the first day ad on a day when there isn’t much fat left.

Like, if you leave a bucket of water where it can evaporate, the level of the water will go down the the same amount every day, regardless of how deep it is. So with a linear graph, you can estimate how long it will take for the water to evaporate, after just a couple of days measurement.

Depends on many factors, one of them being fluid retention which can be a huge problem in the morbidly obese.

As for diets, the “biggest” one I ever saw ordered was 4,000 calories a day. The patient weighed over 500 pounds, and the doctor wanted them to lose weight but not too rapidly. Since it takes about 10 calories per pound per day just to keep a person alive, this would result in a weight loss of several pounds a week. You also have to maintain protein intake to minimize loss of muscle tissue.

I weighed 334 pounds when I started my weight-loss program, so about 152kg, not quite in the ballpark you are positing, but it might be instructive. I lost 150 pounds in 9 months, which works out to an average of almost 4 pounds a week. The first week was 12 pounds but some of that was water weight. Weight loss was faster at first and then slowed down. We were encouraged to exercise and to increase our level of exercise over time, which certainly contributed to the continuing success of the weight loss.

My weight loss program was a doctor-supervised liquid diet consisting of 500 calories a day (they don’t do that any more, now the minimum is 800) of high-protein shakes supplemented with a liquid potassium supplement and at least 64 ounces of water a day. The doctor supervision consisted of blood tests every month and a short doctor assessment every week (weigh-in, blood pressure, interview). There were also mandatory group meetings every week, intended for nutritional education and support in continuing the program.

So for someone as obese as 250kg (550 pounds) I think 5 pounds a week over a long period of time is reasonable, if they are in a similar sort of program; they could reach 200 pounds in 70 weeks at that rate. I would never advise it without the doctor supervision, even though that was probably 2/3 of the cost (the rest being the cost of the shakes).

**jtur88 **- that’s not the way it works. Your body burns less energy as you lose weight. A 550 pound person at rest will probably burn 4500-5000 calories a day just to feed all the body cells he has. A 200 pound person at rest will only burn around 2000 calories a day (assuming a higher ratio of muscle to fat for a slightly higher burn rate). So if you are eating 2000 calories a day, you will lose weight at a rapid rate when you are 550 pounds, and if you reach 200 pounds you will stop losing. This is sort of a simplistic explanation, nearwildheaven is right that it is more complex than that. But it is a useful rule of thumb.

By the way, in the latter case you can either reduce your calories or increase the calories you burn by exercising, or both, to continue to lose weight. Studies show that in long-term and large-scale weight loss, most of the weight lost is through reducing the calorie intake, and exercise helps; with maintenance of weight after weight loss, exercise becomes more important.

The severely obese can lose over a pound of fat day at first. I’ve watched TV shows about people who weigh 600-700 pounds who lose 300+ in a year. I’ve seen some lose 50 pounds in a month. But you risk gallbladder issues and loose skin at those weight loss rates.
A person starting at 550 could probably lose 160-200 pounds in six months if they worked at it.

Don’t try this at home:

I lost 100 pounds in 90 days two different times in my life.

No doctors, no checks.

I am still not dead nor have any gallbladder or kidney problems as a result.

Once about 40 years ago & then again about 35 yeas ago.

Some in prisoner of war camps & concentration camps lost more or even faster. Also should not be tried at home.

So, all you need to do is sharply & clearly define YOUR definition of safely. :smiley:

So when people lose massive amounts of, uh, mass, does the number of cells in their body decrease, or do the cells just get smaller, or what?

Fat cells get smaller; I can’t speak to muscle or organ cells.

Eventually, if you keep the weight off for at least 5 years, the fat cells start disappearing. I have no idea how long it takes to lose all the extra shrunken cells.

Loose skin is a worse problem for older than younger people, just because of the loss of elasticity as one ages. I saw a slide presentation once from a plastic surgeon of a full body lift. They literally pull up your entire body’s skin, cut off the extra, and sew you up. i think they also re-position things like nipples. I guess it works, but you have a scar all the way around your body at the level of your armpits for the rest of your life. This was a solution I decided to forgo, even if I could have afforded it. I kept my floppy man-boobs and belly pouch, and now they have partially filled in again. At my age, I don’t think anyone cares.

Personal reports stated here notwithstanding the studies are consistent that even supervised very low calorie diets (400 to under 800 KCal/d) will start out with a short period of rapid loss but will level out to 0.8 kg/wk.

Given that such is what multiple published documented studies have shown is what is possible on average under the circumstances described, about 20kg or about 46 pounds over the 6 months, that is the GQ answer.

Claims of doing otherwise are inconsistent with what the literature shows will happen.

No, fat cell number, once established, does not decrease, even after years of weight loss. They change size. They do not disappear.

That last statement I made is not completely precise: fat cells (adipocytes) do actually disappear; they are just replaced in similar numbers. Fat mass loss will cause the average cell to be smaller but will not decrease the total number of cells. OTOH fat mass increase, especially early in life, may cause some increase in number as well as in average size. Hence the long term obese may have more fat cells than most lean people and each fat cell may be significantly larger. Fat mass loss will decrease the size of the average cell. Each cell has a limited lifespan; new cells created replace the ones that die.

Intuitively many of us would think that it would be better if we produced fewer new fat cells but some very interesting work suggests that the ability to make more cells more easily is actually somewhat protective: those who produce fewer new fat cells each year (less hyperplasia) tend, at any particular BMI, to have fewer but larger fat cells (more adipocyte hypertrophy) and poorer insulin sensitivity. The concept is that fat cells are to some degree good in that they allow fatty acids to be sucked up there rather than depositied into organs with worse metabolic consequences. Hypertrophied adipocytes have limited capacity to absorb more compared to a greater number of smaller ones.

Bolding mine.

Obviously preliminary work but fascinating and may partially help explain why an obese person who loses a modest amount of fat mass to get to a particular still obese BMI and percent body fat is at less risk of diabetes (etc.) than someone who has gained fat mass to that same level of obesity. Probably not as a big a factor as the fact that fat loss tends to come from visceral fat stores first (especially the more that is already stored there) but still.

Also I do not mean to imply that our posters’ anecdotal reports are untrue. The studies report what occurs on average. Outliers exist and few are exactly average. Our posters can all be those atypical outliers. But the op was asking what is realistic to expect and average is what is realistic to expect. Some more, some less, even on a supervised very low calorie plan.

I can’t access that study, but what was the starting weight of the people losing weight? Someone who starts with 100 lbs of body fat is going to lose weight more slowly than someone who starts with 400 lbs of body fat.

Here’sa go-round. Click the third one down and it calls the whole review article up. Reasonable point that these do not appear to have been exclusively the super-morbidly obese. That said I’d take what you see on tv shows somewhat skeptically.

As anecdotal evidence, following bariatric surgery I lost 104 pounds in exactly 6 months. Suffered no negative health issues and my blood panels were all within acceptable ranges throughout. 70 pounds of of that was in the first three of those months and 25 in the first 17 days following surgery (when I was on liquids only).

But that was on the very high end of the curve of my doctor’s expectations as that was originally the goal for 1 year out. At that speed they suggested I try to slow it down (I wasn’t doing depriving myself more than their plan for me, that’s just how fast it come off) and they did a couple extra panels during to keep an eye on that stuff.

So what DSeid says above seems in line with what my doctor had as average expectations, though individual mileage varies.