Selecting a weight-loss plan can be tricky. Everywhere you look, media reports bombard you with stories about how Jennifer Hudson lost 80 pounds by joining Weight Watchers, Sharon Osbourne shed 23 pounds on the Atkins diet, and other A-listers slimmed down on the Zone Diet. And then there's that close friend who dropped three dress sizes after following the South Beach Diet. How do you determine which dieting plan is the most effective?
To answer this question, Edward Mills, PhD, a visiting associate professor at Stanford, and colleagues completed a network meta-analysis of 48 randomized trials of brand-name diets, which included a total of more than 7,200 overweight or obese adults. In addition to those mentioned above, researchers also evaluated six other diets: Ornish, Vulumetrics, Jenny Craig, Rosemary Conley, Biggest Loser and Nutrisystem. The diets were divided into three categories — low-carb, low-fat and moderate macronutrient.
The diet that a person can maintain for the long term, or for as long as possible, is the most effective weight-loss plan
Overall, the study showed that if people stuck to their diets (no matter the type) they lost weight, but ultimately the "weight-loss differences between individual diets were minimal and largely unimportant," according to Mills. The study authors concluded that the diet that a person can maintain for the long term, or for as long as possible, is the most effective weight-loss plan. They also found that exercise and behavioral support can enhanced weight loss.
Interested to know more about the research, I reached out to Mills, who explained how the evidence failed to support recommending a specific diet and discussed the potential of being able to combine diets to achieve lasting weight loss without having to maintain strict eating habits.
Why did you and your colleagues complete a comparison study of popular diets?
There is a massive weight-loss industry that promotes different diets that are marketed in different ways. Some diets are promoted as being more medical, such as the Ornish diet, while others target people according to lifestyle, for example the South Beach diet. With all the promotion of different diets occurring and people discussing what they believe works or does not work, we wanted to examine whether the clinical trial evidence demonstrated superiority of any particular diet, a strategy we are calling "evidence-based dieting."
In the study, individuals on a low-carb and low-fat diet lost the most weight (8 kg over six months), compared to those who were not on any diet. Why are these diets not considered to be the most effective of those studied?
These diets do appear to offer the largest weight-loss benefits, but the difference between the different diets was so small that other issues begin to be more important. We looked at the diets using two different analyses. First, we grouped diets according to their type of diet, called a class, and then examined whether the individual diet resulted in different outcomes. Although we found differences according to the classes of diets, these were not really observed when we examined the individual diets. So at this point, we can’t recommend any particular diet over another. But those that are low carb or low fat are preferable.
What did you find most surprising about the study results?
What is most surprising about the results is that the individual diet a person chooses doesn't seem to be the most important aspect of dieting, instead maintaining a diet is. Some people have a lot of difficulty adhering to a diet because they find the particular diet too difficult to maintain, such as avoiding carbs if they're trying the Atkin’s diet. It appears that if all diets offer more or less the same benefits, then people should be able to switch between diets when they need to. This approach may be really helpful in adhering to dieting in general.
Given these findings, what should future research focus on to help individuals select an effective weight-loss plan?
I think that future research should look at whether mixing diets results in important improvements. For example, what would happen if you spent a few weeks on a really low-calorie diet, such as a juice diet, followed by a low-fat diet? Is that more important for weight loss than either alone? What about doing a specific diet one week, such as Atkin’s, and another the following week, such as the Zone, and another the following week? Such an approach may be nutritionally more favorable than extreme dieting.
At the end of the day, what we can really conclude is that you should pick a diet or approach that you can adhere to. Whether one offers a small benefit over the other should be considered a minor issue.
Previously: Learning weight-maintenance skills first helps prevent diet backsliding, Stanford study shows, To meet weight loss goals, start exercise and healthy eating programs at the same time, Can a food-tracking app help promote healthy eating habits?, Examining how friends and family can influence our weight loss and Research shows remote weight loss interventions equally effective as face-to-face coaching programs
Photo by Allan Foster