Nutritional Pearls: Which Diet Is Best For Weight Loss?
Patrick is a 28-year-old man with a body mass index of 31 who has struggled with his weight for most of his life.
Patrick has tried several popular diets over the years, including vegetarian, low-carb, low-fat, and the paleo diet, but has struggled to maintain each diet for more than a few weeks at a time.
He asks you if there is any effective, popular diet that would allow him to continue to enjoy the meals he likes, but also help him to lose weight.
How do you advise your patient?
(Answer and discussion on next page)
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Answer: A Mediterranean-style diet allows people to eat what they like while also eating healthy.
There's a lot of controversy over which diet is best if you want to lose weight. Low fat? Low carbohydrate? High fat? Mediterranean Diet? DASH (Dietary Approaches to Stop Hypertension)? Weight Watchers? Jenny Craig? Vegetarian? Vegan? Omnivore? Pescetarian? The list is endless, and people will argue for their favorite diet with zeal.
Studies pop up all the time that seem to show that one type of diet helps people lose weight faster than another type of diet. Unfortunately, many of the studies that compare one diet to another are poorly designed, limit people's food choices in unsustainable ways, or both.
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A team at the Veterans Affairs Medical Center in Durham, North Carolina took the approach that rather than being prescribed a specific diet, for the purposes of weight loss alone people might do better and lose more weight if they could choose the diet themselves.1 While this makes logical sense, just because something "makes sense" doesn't mean it holds up to controlled trials.
The Research
About 200 male and female veterans were recruited from Veterans Affairs patients in Durham. All participants were otherwise healthy but were considered clinically obese (having a body mass index over 30). Half the patients were assigned to a "choice" group and half to a control group.
Those in the choice group responded to a dietary preference questionnaire, which allowed the staff to recommend either a low-carb or low-fat diet based on their existing preferences. The choice group participants were then able to choose for themselves which diet they would follow for the next 12 weeks. After 12 weeks of following that diet, they were given the opportunity to switch to the other diet.
Those in the control group were randomly assigned to either a low-fat or low-carb diet for the duration of the 24-week study.
Both groups received regular personal and group counseling sessions to help with goal setting and problem solving, and the individual's adherence to their assigned or chosen diet was measured by regular dietary questionnaires. Those on a low-fat diet were to consume no more than 30% of their calories from fat and to cut their total caloric intake by about 500 calories per day. Those in a low-carbohydrate diet were to consume no more than 10% of their calories from carbohydrates, but had no specified calorie restriction.
Very few of the choice participants decided to switch to the other diet after the initial 12 weeks: only 5 people out of 105 decided they were unsatisfied with their chosen diet plan.
The Results
The results are very interesting: those in the choice group lost, on average, about 5.7 kilograms (about 12.6 pounds), while those in the control group lost an average of 6.7 kilograms (about 14.8 pounds).
If we're looking at overall weight loss, statistically speaking it didn't matter whether people chose their diet or not—they still lost about the same amount. What did appear to make a difference was how many counseling visits people attended: those who attended at least 15 session lost about 3 times as much weight as those who attended fewer than 15 counseling sessions.
This supports what I've been saying for years: that it's the diet you can stick to for the long term that will work best for you. For some individuals, that's low-carb or low-fat or vegan-no-oil, but for the vast majority of people, a Mediterranean-style diet of a variety of high-quality carbohydrates, moderate meats, and lots of fruits and vegetables is the one that is going to allow people to eat what they like while also eating healthy.
Reference:
1. Yancy WS, Mayer SB, Coffman CJ, et al. Effect of allowing choice of diet on weight loss: a randomized trial. Ann Intern Med. 2015;162(12):805-814