As RDs, we know that success in treating clients with overweight and obesity depends on individualized diet and lifestyle recommendations.
A move in the research community toward understanding individual differences in weight loss occurred in the 2017 DIETFITS (Diet Intervention Examining The Factors Interacting with Treatment Success) study. The primary aim of this investigation was to identify the variety of factors influencing participants at baseline that may help explain weight loss differences when individuals are assigned to the same diet. Rather than seeking to determine whether one dietary approach was better than the other for the general population, it sought to examine whether greater overall weight loss could be achieved by matching different people to different diets.
To shed some light on this study and how commercial weight loss companies are implementing programs in response, RD Lounge (RDL) speaks with Courtney McCormick, MPH, RDN, LDN, manager of Clinical Nutrition & Research at Nutrisystem, and LeeAnn Kindness, MS, product manager at Nutrisystem, to share their thoughts.
RDL: Can you shed light on the results of the DIETFITS study and the implications for weight loss programs?
McCormick & Kindness: One of the biggest takeaways from the DIETFITS study was that this continues to add to the evidence base that there really is not a “best dietary approach” when it comes to weight loss. There are many different dietary approaches that will lead to successful weight loss (ie, clinically meaningful weight loss). Some people will respond well to a low-fat diet, while others may respond better to low carb.
But the study did point to a few common themes across both dietary patterns, which can (and should) be included in any approach to weight loss. These include things like eating more vegetables, including nutrient-rich minimally processed foods, and reducing intake of added sugars.
RDL: What are the implications for commercial weight loss programs?
McCormick & Kindness: Weight loss programs do a really great job at helping people lose the weight. Where there needs to be more focus among weight loss programs is a better understanding and integration of the science around what predicts one’s success at maintaining that weight loss. A body of evidence suggests that greater adherence to diet is a better predictor of long-term weight loss success than the type of diet. And, an emerging body of evidence is starting to tell us that one way to get people to better adhere to a specific dietary pattern that supports health is to personalize it to match their preferences and lifestyle.
RDL: Can you discuss the science behind personalized weight loss approaches, including factors such as body type, that can be used to individualize weight loss?
McCormick & Kindness: Weight loss can be, and should be, personalized to support everyone’s unique metabolic needs. Weight loss activates the body’s self-defense system where metabolism slows during caloric restriction to defend against starvation. This defense is focused on restoring the body’s depleted energy stores. Every time you go on a weight loss diet, you are activating this self-defense system to limit energy depletion, and this is called metabolic adaptation.
We’ve seen in the research that in people who follow weight loss diets, especially frequently and for long periods of time, or take their calories too low, their [basal metabolic rate] is much lower than it should be. People usually find that it’s easy to lose weight initially during a weight loss diet, but eventually, your metabolic rate slows to adapt to the calorie deficit. On average, the metabolic adaptation is about 10% to 15% but sometimes can be far more extreme (up to 35%).
This tells us that in order to set people up for the best chance of long-term success, we must individualize caloric needs on a weight loss plan, and that their caloric needs will change over the course of their weight loss, so plans must be revisited and adjusted as needed for sustained weight loss (avoidance of plateaus).
RDL: What does the science say about factors that might help predict who will be successful on one dietary pattern or another, and what factors may help lead to improved health outcomes on one dietary pattern over another?
McCormick & Kindness: Obesity is a complex, complicated chronic disease, and in order to deliver optimal obesity care we must go beyond the simple mentality of changing behavior to tip the balance of calories in and calories out. We need to think at the individual level and think about how one’s individual physiology may impact their energy balance.
As we’ve seen from DIETFITS and other research, many dietary patterns can help us achieve weight loss. But it is important that we think beyond just weight loss and think about a weight loss approach that will optimize our health outcomes. For example, where an individual stores excess fat may help predict what dietary approach will best deliver on weight loss, but also optimize health outcomes through improving the individual’s metabolic profile. There is an association between body composition (ie, where one stores adipose tissue on and within the body) and metabolic outcomes (eg, insulin sensitivity), which play a direct role in the efficiency of carbohydrate and fat metabolism. Whether a person presents with more adipose tissue around the abdominal area vs the buttocks, hips, and thighs, can predict what metabolic abnormalities may be present in that individual. Knowing that individuals who carry excess adipose around their mid-section are at increased risk of metabolic syndrome, we can predict that having them adopt a dietary approach that focuses on the quantity and quality of their carbohydrate choices may have a bigger impact on health outcomes.
While one-on-one counseling for weight management is preferred to maximize the individuality of interventions, this counseling format isn’t possible logistically or financially for many. Commercial weight loss programs are evolving to meet the demands of consumers looking for a more personalized approach, and it’s important that RDs are aware of what’s available for our potential clients.
— Lauren Harris-Pincus, MS, RDN, is a nutrition communications specialist, speaker, spokesperson, in private practice, and author of The Protein-Packed Breakfast Club. Lauren blogs at www.NutritionStarringYOU.com, where she specializes in weight management and prediabetes.