Why do weight loss studies always put people on crazy diets?

December 7, 2018 3:40 PM

The conventional wisdom is that people who lose weight never keep it off. Yet every time I see a weight loss study quoted to back this up, it turns out people were put on some sort of crazy drastic diet. Why do obesity researchers think this gives a valid read on how easy it is to maintain weight loss?

I was just reading this article in the New York Times. I quote:

"Scientists got an unsparing look at what they were up against 50 years ago, when a clinical researcher at Rockefeller University, Dr. Jules Hirsch, did some old-fashioned experiments. He recruited obese people to stay at the hospital and subsist on a 600-calorie a day liquid diet until they reached a normal weight.

The subjects lost 100 pounds on average, and they were thrilled. But as soon as they left the hospital, the pounds piled back on."

Why would you not gain it back if you lost it eating only 600 calories a day? I mean this is not what people recommend generally, and it just seems logical that as soon as the diet was over you'd reach for the food again after being deprived. Is there an actual scientific reason people run weight loss studies like this?

posted by knownfossils to Health & Fitness (10 answers total)

every time I see a weight loss study quoted to back this up, it turns out people were put on some sort of crazy drastic diet

Studies that make it into the lay press usually have either crazy methods ("keep obese people in the hospital on a 600-calorie liquid diet") or significant results ("these people lost weight and kept it off forever!"). There are virtually none of the latter in the realm of weight loss, so rather than report uninteresting results, the lay press will always favor the studies that sound "crazy."
posted by telegraph at 4:21 PM on December 7, 2018 [4 favorites]

Well, how do you have this knowledge? What was the conventional wisdom among doctors and researchers 50 years ago? The reason you are so confident about what would happen is because in part researchers have tried this and documented the results. Conventional wisdom, what we think we all know, changes a lot over time. Let's hope it's at least in part because of the results of research.

I'd like to push back against the idea that weight loss studies "always" put people on "crazy diets." Maybe that's what you see reported in the popular press. Maybe the studies about 1500 calorie diets and supplements aren't interesting enough for the New York Times to report on. Are you familiar with the idea of confirmation bias?

(On preview: what telegraph said.)

Also, please note that the Times article is talking about a research study done 50 years ago, and then repeated to make sure the results were valid.

There's a medical journal called Obesity Reviews. You can scan the list of articles to see a range of research studies recently conducted.
posted by bluedaisy at 4:27 PM on December 7, 2018 [5 favorites]

I was in a weight loss study. I was put on Weight Watchers for a year, which is hardly a drastic weight loss diet.

I also put the weight back on. Very slowly for a few years but last year I gained 10kg and ended up right back where I started. Even I'm not sure why I couldn't maintain my lower weight.

Anyway, weight loss studies try different techniques because they are trying to find out what works. 600 calorie might have worked, they tested it and found out for most people it didn't end up in making a permanent change. I assume for their next study they tried something else.
posted by antiwiggle at 5:13 PM on December 7, 2018 [1 favorite]

I don't think the studies always put people on crazy diets. Those diets are just the ones that make it into articles like this as examples of things that don't work. It's a pretty obvious straw man to knock down: "Of course things like this don't work. Why would researchers ever think that?" But as antiwiggle notes, someone has to try these things in the first place so we know whether they work. If only 600 calories of smoothies per day actually worked, don't you think everyone would want to know that?

I do think this article isn't particularly well-targeted in its scope. It's not saying much of anything new, there doesn't even seem to be a timely hook, and as noted, it uses some poor examples as straw men.


There is just one almost uniformly effective treatment, and it is woefully underused: only about 1 percent of the 24 million American adults who are eligible get the procedure.

Yeah, most people don't really want to have surgery to turn their stomach into a pouch and/or reroute their intestines, surprise! Especially not when one generally has to lose weight before the surgery just to qualify for it, and it carries serious long-term risks. "Woefully underused" is really a bit of editorializing, and seems a tidge victim-blamey, too.

This article also doesn't even talk about epigenetics, whereby one's DNA can activate in entirely different ways, depending upon the life experiences of one's grandparents and great-grandparents. The grandparents and great-grandparents of many people alive today in the U.S., for instance, lived through at least the Great Depression, at least one world war, and in many cases things like pogroms in other countries—periods of major trauma and starvation. As it turns out, that quite likely has an epigenetic effect on the current "obesity epidemic," and to me, that's some of the most interesting science out there in this area right now.

Here's a better article on this subject. I would definitely suggest checking it out!
posted by limeonaire at 7:31 PM on December 7, 2018 [6 favorites]

Researchers need to see some weight loss effect within the timeframe they’re funded for (not usually the year or more sane weight loss often takes) - like 12 weeks or so. At 1200 calories a day, women can expect to lose 2 lbs a week. They’ll starve and suffer, but they’ll see results relatively quickly. At 1800 calories, they’ll lose with less pain, but it won’t fit into the study timeline.
posted by cotton dress sock at 8:31 PM on December 7, 2018 [4 favorites]

That’s quite an assumption you’ve made reading one article. Don’t do that. The press often misconstrues and over simplifies the results of scientific studies and also often quotes or writes stories about scientific studies commissioned by mega corps that are designed to mislead the public. If you want more insight into the link between weight loss and weight gain and dieting, try reading Health At Any Size. It covers the link between food restriction and the reward centres in your brain, as well as more long term studies, and how the media has confused the science in many places.
posted by pazazygeek at 12:08 AM on December 8, 2018 [1 favorite]

People are paying and they want fast, visible results. The therapeutic community makes money by offering the results. Often people are seriously ill and need treatment, once it is done, the dieters have to hold the line. The most acutely unpleasant part of the process is starving the weight off, and the internal dialogue that goes with it. The therapeutic community provides back bone to make it happen and since people are paying they stick with it. Maybe they don't pay in some studies, but whatever the study, the practitioners are usually creating the results they want.

Radical diets that work speed the most painful part of the process. Maintenance is about finding internal rewards for the new body facility, appearance, ease of use. It is also about reestablishing relations with muscle activity, and renewed stamina. Then the task is also realizing how much energy a person can consume daily to stay fit, and enjoy mealtimes. We can live on a whole lot less than we do, and maintain optimum health. The hardest part of dieting is listening to the complaining and wheedling, bargaining, and general neediness of your own biome. Own is the operating verb, owning, managing then loving the process of eating and exercising to live well and maintain optimum health and joy

People who opt for surgery will be on 500 calorie a day diets for life, a lot of them get major surgery and gain the weight back.
posted by Oyéah at 9:54 AM on December 8, 2018 [1 favorite]

My previous comment was deleted, let me try again....
Extreme restriction diets are effective when combined and followed up with long term lifestyle changes. Here's a harvard article on a study that did just that - very low carb compared to very low fat, both were effective as they got people to adjust to reduced calorie intake and getting the recommended exercise time per week.
posted by JonB at 10:37 AM on December 8, 2018

Is there an actual scientific reason people run weight loss studies like this?

Yes, there is: a lot of scientific experiments are designed to test a specific hypothesis, not to find something that works in practice. Experiments are often conducted under extremely controlled circumstance that do not look like real life, so that the exact impact of the phenomenon under study can be isolated as much as possible. In nutrition, a lot of the effect sizes of dietary changes are very small, and may take a long time to have an impact, so if you have only a short time to study a change, you might have to do an extreme intervention.

For example, a diet and nutrition study might ask a question like "what is more important for weight loss, fat or carbohydrates?" To answer this question, you might design an experiment that fed one group of people a diet with no carbs and tons of fat, and the other no fat and tons of carbs, to see whether you could produce any difference at all in a few weeks. If you do find a difference, you have gained insight into the relative importance of fat or carbs, though neither experimental diet is practically useful. Then you can build on this insight and ask a question like "which low-carb diet will actually help people in the real world lose weight and keep it off for more than a few weeks?" This, of course, is a much harder (and longer) study to run.

I'm not sure exactly which study the NYT was referring to, but his original question was probably something like "What happens to obese individuals' fat cells after they lose a lot of weight? Do they shrink or do they go away?" The study was designed to answer this question, not test a practical diet.
posted by googly at 5:29 PM on December 8, 2018 [2 favorites]

The premise here is not correct -- weight loss studies do not always involve "crazy diets." There are many different types of nutritional/weight loss studies, designed to examine different outcomes. Some examine extreme calorie restriction, or extreme macronutrient manipulation, but not all. Some are short-term inpatient studies, where intake and energy expenditure are tightly controlled and measured; others are longer-term outpatient studies that more closely resemble a "real-world" scenario, but where precise measurement of those types of variables is more difficult. Here's one example of the latter type of study (811 patients, followup over 2 years).
posted by ludwig_van at 12:05 PM on December 9, 2018