The New Thinking About Weight Loss

As a psychologist involved in treating eating and weight problems, I’m an avid reader of scientific journals to keep up with new research. Although it may be uncomfortable, I find myself having to revise opinions that I had expressed in workshops, books, and articles. If you’re weight-conscious, it’s hard to know what to think when something presented in the media conflicts with previous advice you’ve accepted. Here are a couple of examples of my beliefs that have been challenged by recent research.

1. I thought that dieters should set realistic goals for gradual, sustainable weight loss. It makes sense: Drastic changes in diet would be hard to maintain after the initial burst of enthusiasm wears off. Making gradual changes in eating should be easier.

An Australian study challenged this belief. Researchers told 100 volunteers to cut their usual food intake by 500 calories per day aiming for a pound per week weight loss. Another group of dieters consumed only 450 to 800 calories a day, all from meal replacement drinks. The goal for both groups was to lose 15 percent of their weight. The slow group had nine months to accomplish this while the rapid group had to do it in three months. Seventy-eight percent of the rapid group met their goal but only 50 percent of the slow group did. The researchers suggested that losing weight quickly might increase motivation to stick with the program.

A three-year follow-up found there wasn’t any difference: Both groups had regained most of the weight they had lost. Long-term it might not make any difference, so if you’re going to diet, choose whichever strategy you think would work best for you.

2. Previous research suggested that eating nuts can help with weight loss (see my “Hungry? Need a Snack?” blog post from 2019). I confess: I like almonds. If I’m hungry in the middle of the afternoon I’ll frequently grab a handful to tide me over until dinner. While almonds and some other nuts are more likely to produce satiety (feeling satisfied) compared with other snacks, new research suggests that nut consumption may not help with weight loss.

The earlier studies were mostly correlational; they observed differences but didn’t demonstrate cause-and-effect relationships. In a new experimental study, researchers in San Diego assigned overweight participants to either a four-month behavioral weight-loss program or the same program with a daily prescription to eat one-and-a-half ounces of pistachio nuts. After four months the pistachio group had a significant reduction in blood pressure. They increased their fiber consumption while eating fewer sweets. Those were benefits from nut consumption but the groups had equal weight losses and similar reductions of BMI and waist circumference.

The new study suggests that snacking on nuts is still a healthy way to deal with between-meal hunger, especially if it replaces junk food—but don’t count on nuts for weight loss.

Research can guide our weight loss efforts but keep in mind that it will be some time (if ever) before there’s a consensus on the best methods. If a new finding resonates with you, give it a try but be open to revisions as new findings emerge.