When dieting doesn't work

At any given time, more than a third of Americans are on a specific diet, with weight loss as a leading reason. Most are going to be disappointed, because even when successful, lost weight is frequently regained within a few months.

While most weight-loss diets can help you lose weight, they may be unsuccessful over the long run for a number of reasons. Some people don't follow their diets carefully and don't lose much weight even from the start. Others may go off the diet entirely after a while, because it's too restrictive or the foods aren't appealing. Some may engage in less physical activity as they consume fewer calories. But who hasn't heard of someone doing everything right and still losing minimal weight, or regaining lost weight over time? Perhaps that someone is you.

Even when research studies confine study subjects to a research setting — with carefully-controlled calories, food types, and physical activity, and with intensive counselling, teaching, and monitoring — the lost weight and other health benefits (such as improved cholesterol and reduced blood pressure) tend to disappear soon after the study ends.

You can't pick the right diet if none of them work

According to a new study, popular diets simply don't work for the vast majority of people. Or more accurately, they are modestly effective for a while, but after a year or so the benefits are largely gone.

In a large systematic review and meta-analysis, recently published in the medical journal The BMJ, researchers analyzed 121 trials that enrolled nearly 22,000 overweight or obese adults who followed one of 14 popular diets, including the Atkins diet, Weight Watchers, Jenny Craig, DASH, and the Mediterranean diet, for an average of six months. The diets were grouped into one of three categories: low-carbohydrate, low-fat, and moderate-macronutrient (diets in this group were similar to those in the low-fat group, but with slightly more fat and slightly less carbohydrate). Loss of excess weight and cardiovascular measures (including cholesterol and blood pressure) while on one of these diets were compared with other diets or usual diets (one in which the person continued to eat as they usually do).

While weight, blood pressure, and cholesterol measures generally improved at the six-month mark, results at the 12-month mark were disappointing, to say the least.

• While low-carbohydrate and low-fat diets both resulted in weight loss of about 10 pounds at six months, most of the lost weight was regained within one year. People in the moderate macronutrient group tended to lose less weight than those following the other diets.
• Blood pressure and cholesterol results improved modestly at six months, but generally returned to where they started after a year. One exception was noted: reduced LDL ("bad") cholesterol levels while on the Mediterranean diet persisted at one year.
• There were no major differences in other health benefits between the various diet programs.

All is not lost

Based on this new report, you might be tempted to throw up your hands and give up on weight-loss diets altogether. But there's another way of looking at this: it probably matters less which plan you pick (whether low-carb, low-fat, or something in between) than whether you stick with it.

The average duration of the studies included in this analysis was six months. What if they'd lasted 12 months, or two years, or a lifetime? The benefit would likely have been greater and more long-lasting. The trick is to pick a diet with foods you actually like so that it's not so hard to stick with it.

In addition, there are factors other than diet that can have a big impact on weight. For example, everyday physical activity, regular exercise, and sleep are important in helping to maintain a healthy weight.

Rather than following a highly restrictive or named diet, I endorse the Mediterranean diet. It's among the best studied, performs well when compared with other diets (as in this analysis), and was the only diet in this analysis to have long-lasting effects on LDL cholesterol levels.

The bottom line

Losing weight is not easy. If you're struggling with your weight, talk to your doctor, a nutritionist, and perhaps a health coach. Review this study with them and, together, decide on dietary and other lifestyle changes that appeal to you. Then stick with them. Remember, you're most likely to stick with lifestyle changes you actually like.

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