Taking Weight Loss Supplements Could Backfire

Losing weight is not easy. Even for those who don't have significant obstacles to weight loss, like those taking certain medications or with certain conditions, it takes a certain amount of discipline to watch portion size, make healthier choices (most of the time), and exercise faithfully. So I understand why people want to take weight-loss supplements. Unfortunately, there are no weight-loss supplements that have been clinically proven to work by being subjected to large-scale, controlled human subjects trials that have been published in peer-reviewed medical journals. (It's true that one might argue that some have: they're available by prescription only.)

Proof aside, a survey in 2005 estimated that 33.9% of United States adults who were trying to lose weight had used weight-loss supplements, totaling over $1.6 billion in sales that same year. Yet about the same percentage of US adults are still overweight or obese. What gives?

Part of the problem may lie in a concept known as "liberating," in which actions that represent progress toward a goal may liberate that person to pursue other, competing goals. Here's a good example: people asked to test a cookie described as "healthy" (the goal of eating healthfully) will eat more of those cookies than those asked to test the same cookie described as "tasty" (the goal of eating things that taste good). With that in mind, a team of researchers in Taiwan designed a study to look at whether people's weight-loss behaviors were affected by taking a weight-loss supplement (Appetite 2014;72:8-12).

Seventy-four men and women who wanted to lose weight but were otherwise healthy were recruited from the local area. Half of the participants were assigned to receive a weight-loss supplement, and half received a placebo. (In actuality, all of the participants received the same placebo.) After being assigned, the participants were given the pills, told what the pills were (whether a "weight-loss supplement" or a placebo) and asked to rate their perception of the pills in terms of color, size, shape, texture, and flavor. As part of a general questionnaire, the subjects were asked to rate how well they felt they were progressing toward their weight loss goal.

In a later visit to the lab, the participants were asked to participate in a further taste test. Before the test started the researchers informed them that they would receive a reward drink after the test, a popular local drink known as bubble tea. The participants filled out an order form specifying the amount of sugar they wanted added to their reward drink and returned the form to the researchers for delivery after the test. Finally, the participants were asked to evaluate two different flavors of common candies, which were presented in two bowls containing the same number and weight of each candy. They were encouraged to eat as many candies as they wished, and the amount of candy each person ate was recorded at the end of the study.

The researchers found that those who believed that they had taken a weight-loss supplement were more likely to choose a greater amount of sugar for their reward drinks, and tended to eat more candies, while at the same time believing more strongly than those taking the placebo that they were making progress towards their weight loss goal.

What this means for you

This isn't really about weight-loss supplements at all: it's a reminder to keep your eye on your goal, whether that's simply making healthier food choices or losing weight. This study shows how easy it can be to sabotage your positive efforts by giving yourself license to make poor choices after making good choices. Make sure your good choices vastly outnumber your poor choices: that way you'll make steady progress toward your goal.

First posted: October 23, 2013