What If Everything You Know About Weight Loss Is Wrong?

What If Everything You Know About Weight Loss Is Wrong?

One major review gets to the bottom of some of the most popular weight loss claims. Here’s what you need to know.

Why is it so hard to lose weight? Here’s one reason: A lot of what we all take for granted about weight loss is unproven or flat-out wrong. That’s the bottom line from a special article published in 2013 in the New England Journal of Medicine. The article laid out what works and what doesn’t, and detailed the commonly held weight loss beliefs that are not supported by research. The review also unveiled some of the theories that have not been proven or disproven. Here are some of the most surprising theories, plus what science really says about them.  

Theory:  Having a realistic weight-loss goal will keep you motivated.
Sadly, this idea is not supported by evidence. In fact, several studies have shown that people with very ambitious goals (for example, those on the show, The Biggest Loser) end up losing more than people who aim lower.

Theory: Slow but steady weight loss is best for long-term success.
Many physicians have long believed this to be true—I know I did. But a review of many long-term trials found not only that a very-low-calorie diet resulted in significantly more weight loss after six months (16 percent of body weight versus 10 percent lost with a more moderate approach), but those differences in weight loss persisted up to 18 months!

I’ve never been a fan of very-low-calorie restrictive diets, but apparently the weight loss is maintained in many cases. However, if you want to go very low calorie, it’s important to get guidance from your doctor or a registered dietitian.

Theory:  Small changes will produce big results.
This idea was based on the fact that 3,500 calories equals 1 pound of weight, which suggests that if you cut 500 calories out of your meals each day, burn an extra 500 calories through exercise or do a cut-and-burn combo, you should lose a pound a week. But that equation doesn’t take into account the fact that as you lose weight, your need for “fuel” goes down— just as a smaller car generally needs less gas per mile than a bigger one. That means that as you lose weight, you need to exercise more and eat less just to keep losing at the same rate.

Theory: A bout of sexual activity burns 100 to 300 calories.
It’s sad to debunk this myth, but here we go. With intense sexual activity, a 154-pound man burns approximately 3.5 calories per minute. This may be TMI, but research tells us that the average time spent during one “stimulation and orgasm session” is about 6 minutes—meaning that the 154-pound man might expend about 21 calories total. But he’d burn about 7 calories just lying on the couch, so subtract that amount…and you end up with sexual activity burning a grand total of 14 calories. Bummer.

While the above theories were myths according to the review, some other theories were more like presumptions, or widely accepted beliefs that have neither been proved nor disproved, says study authors. Here’s a look at those:

Theory:  Eating breakfast prevents obesity.
Fact: Several studies showed that people were no more likely to lose weight if they regularly ate breakfast than if they were breakfast-skippers.

Theory: Adding fruits and vegetables to your diet results in weight loss.
Adding more calories of any type without making any other changes is likely to cause weight gain. Fruits and vegetables are great for your health, however, so I certainly wouldn’t recommend against it—the key is to eat them instead of less healthy, higher-calorie foods.

Theory: Yoyo dieting" increases mortality
Fact: There is no evidence that this is true.

Feeling a little lost now that everything you took for granted about losing weight has been yanked away? The good news is that the journal article didn’t just focus on what’s not true – it also featured weight-loss advice that is supported by research.

Medically reviewed in September 2019.

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