Stanford Medicine Newsletter Updates For the Local Community

 

The keys to dieting success

An interview with Christopher Gardner

Christopher Gardner

   

Many dieters face a dilemma when they're trying to lose weight: Will a low-fat diet work best, or should they try the low-carb approach? Nutrition expert Christopher Gardner, PhD, professor of medicine at the Stanford Prevention Research Center, wanted to provide some answers.

For one year, his team tracked 609 overweight people who were assigned to follow either a healthy low-fat diet or a healthy low-carb diet. The team hoped to determine whether a dieter's genotype patterns or insulin levels could predict which diet would work best.
Neither of those factors predicted diet success as hoped, but Gardner and his colleagues found that some of the participants in both groups were able to lose weight by changing their relationship with food.
Gardner discussed his recent diet study and his recommendations for losing weight in an interview with Stanford Medicine News.

Q: Why did you want to find out whether a person's genetics or insulin levels could indicate whether they'd lose more weight with a low-carb or a low-fat diet?

Gardner: We had some hints from past studies that both of these factors might help explain part of the massive variability that is consistently seen in weight-loss research studies. For example, in a typical weight-loss study, some participants lose up to 50 or 60 pounds, while a few gain weight. Data from a pilot study suggested that a person's genotype patterns and blood insulin levels could be helpful in predicting which people were more likely to lose weight on a particular diet. After 12 months of following 609 overweight and obese study participants who collectively lost more than 6,500 pounds, we found that neither of those factors helped to explain the range of differential weight change response to either the healthy low-fat or healthy low-carb diets. We were not able to predict which diet was best for whom, as we had hypothesized.

Q: Should we focus on what type of diet — low-fat or low-carb — we want to follow, or are there other weight-loss strategies that are more crucial to consider?

Gardner: Our study results suggest that it would likely be better to focus on foundational aspects of food habits first. During our yearlong study, the healthy low-fat group was advised to emphasize foods like steel-cut oats and lentils and to limit high-carb foods, and the healthy low-carb group was told to emphasize foods like nuts, seeds, avocados and salmon while limiting their consumption of fats.

Both groups, though, were told to maximize their intake of vegetables (particularly non-starchy vegetables), to minimize added sugars and refined grains, and to choose whole foods rather than highly processed foods. Both groups were also advised to work on "mindful" eating, which involved things like not eating in the car, not eating while looking at a TV or phone screen, cooking more for themselves at home, and eating more sit-down meals with family or friends. Therefore, some of the strategies that applied to both groups — the foundational aspects of food habits — were helpful for most of the participants who lost weight.

Additionally, participants were asked to think in terms of "eating plans," meaning that they could adopt these new behaviors for years to come, rather than thinking about "diets," which most people follow for a short time and then abandon.

Q: What changes were made by the most successful dieters in your study?

Gardner: Our five health educators, who held 22 evening class sessions for the study participants during the year, had a lot of contact with the participants. One consistent theme we heard from the participants in both diet groups who lost 20 to 60 pounds was that we had "changed their relationship to food." Although the study was not designed to test this specifically, we would like to explore this secondary finding in future studies.

Q: What are the best ways of changing our relationship with food?

Gardner: The single descriptor that best captures this is mindfulness, which is the opposite of mindlessness. With 24/7 accessibility of foods, and a global food system that makes it possible to have any food you want delivered to you in ever more convenient and time-saving ways, it has become easier and easier to eat and drink without really thinking about it — mindless eating.

Mindfulness involves not eating while looking at a screen, and not eating while driving or walking or in a store. Mindfulness includes cooking more meals for ourselves; shopping for fresh, whole foods at the local farmers' market; and sitting down and taking the time to enjoy meals and eating occasions with friends and family. It means bringing back some of the food literacy and culinary literacy that has been lost with the relentless increases in "convenience." Taking a greater interest in the external and societal costs that come with our food choices — in terms of potential human labor abuses, animal rights and welfare, and environmental sustainability — contributes importantly to mindfulness and to changing our relationship to food.

Q: Will science ever give us an answer about the "ideal" diet, or is that hoping for too much?

Gardner: I'm happy to tell you science already has provided an answer about the "ideal" diet. But I'm frustrated to say that even though this information is out there, and has been for decades, it isn't recognized or appreciated. Health professionals agree that the majority of our diets should come from whole, plant-based foods — vegetables, beans and legumes, nuts and seeds, whole grains, and fruits — and most of us should cut back on meats and dairy, and especially on convenience foods that tend to be heavily processed and that contain addictive combinations of salt, sugar and fat.

When a healthy foundation is set, there is plenty of room for individuals to find their own favorite, personalized diet approach by dialing certain things up and down. There are many ideal diets waiting to be enjoyed — if we can get the foundational principles right.

Clinical trials such as this one are made possible by the participation of community members, both those who are healthy and those with specific conditions. Information about participating in clinical trials at Stanford is available online.

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