9 surprising facts about weight loss.

In my last post, I talked about the importance of behavioral change in preventing early death. This post is the first in a series looking at the evidence behind changing health-related behaviors.


It seems like every other commercial is for a product promising miraculous weight loss. If you’ve ever wondered what actually works, you aren’t alone. In fact, there was an article in the New England Journal of Medicine entitled “Myths, Presumptions, and Facts about Obesity.” That’s right, there is so much misinformation floating around that the authors felt that doctors needed things spelled out more clearly. I picked a few of these ideas out of the article to give you a flavor of what the best research is currently showing.

There is a caveat here. This article is entirely based on results confirmed in randomized controlled trials. That means that each of these facts has been demonstrated by randomly assigning people to groups, providing a different intervention to each group, and then measuring predetermined outcomes. It’s a slow, expensive process, but results from randomized controlled trials are the strongest form of medical evidence, which means that these observations typically trump experiments that happen in test-tubes, animals, or simpler human studies. I’m confident that there are exceptions to all of these rules, and that our understanding of these results will become more nuanced as we gather more data. But for now, these facts are based upon the best data we have.

1. Small sustained changes don’t necessarily produce large, long-term changes in weight.

You’ve heard the mantra: one pound of fat produces 3500 calories of energy. Therefore, if you decrease your caloric intake or increase your exercise by just 100 calories per day, you’ll lose about a pound a month so long as you keep doing that. But the data don’t support this notion. Initially, you will see this level of weight loss, but your body is remarkably effective at keeping your weight where it is. As you lose weight, your body requires fewer calories, making it harder to lose weight if you remain at the same caloric intake. While you might expect to lose 50 pounds over 5 years by cutting out 100 calories a day, studies predict that you’ll probably only lose 10 with this strategy.

2. Weight loss goals don’t need to be realistic to be effective.

Setting a realistic goal gives you a more realistic expectations about how much weight you will lose. That’s nice, but it has no effect on the amount of weight you will actually lose. In fact, some studies suggest that people with ambitious goals tend to lose more weight than those with more modest targets.

3. There is no advantage to trying to lose weight slowly. 

Slow and steady wins the race, right? Not with weight loss. In the short term, people who lose weight more rapidly lose more than people who lose weight slowly. In the long term, both groups tend to lose about the same amount of weight.

4. Weight gain and loss are influenced by both genetic and lifestyle factors.

There is absolutely a genetic predisposition towards obesity. That has become increasingly clear over the last few decades. However, genes are only one variable in the obesity equation. Lifestyle plays a significant role in your weight. And unlike your genes, you do have some level of control over your lifestyle.

5. Diets often work for short-term weight loss, but don’t expect the results to stick around for long.

Enough said. You already knew this, didn’t you? :)

6. Exercise is good for you even if it doesn’t result in weight loss.

Exercise is good for you! In the right dose, it is a well established tool for maintaining a healthy weight. But even if it doesn’t help you shed pounds, exercise is valuable for fighting off some of the ill effects that come from excess weight.

7. If you’ve lost weight and want to keep it off, your best bet is to continue your current weight loss program.

If you want to keep the weight off, you have to keep doing what you are doing. In this sense, obesity is a chronic condition, in that it must be managed through long-term behavioral change. More than anything, I believe that this is the reason obesity is so hard to treat.

8. Structured meal planning (including meal replacements) can be effective tools for weight loss.

While eating a balanced diet containing a variety of foods is sure to be exciting and delicious, this strategy alone is not very effective for weight loss. Consciously choosing to eat less in a structured manner, however, does work. There are a million products that will offer to do this for you and the principle behind them is sound. Deciding which one (if any) is best for you is an entirely different matter.

9. For the right person, bariatric surgery can produce long-term weight loss and a longer life.

Have you ever heard of a gastric bypass, lap band, or stomach stapling? It turns out that these interventions actually work. They are certainly not for everyone, and they come with a litany of potentially awful side effects. However, in the right person, these procedures are almost miraculous. Some critics will tell you that choosing bariatric surgery is “taking the easy way out.” Nothing could be further from the truth. Bariatric surgery requires an incredible commitment to a strict dietary program and prolonged nutritional supplementation. It may enforce dietary changes through increased satiety and horrible symptoms after binge-eating, but it does not in any way represent an easy way to weight loss. Choosing bariatric surgery is not a moral failing. These patients are incredibly courageous. They take drastic measures to improve their health, and I have nothing but the highest respect for anyone who receives this intervention.

I’ll go into more depth about many of these ideas in the future. For now, I highly recommend that you just read the paper. And since the paper isn’t behind a paywall, you really don’t have any excuse not to!