Resources

  1. Christopher D. Gardner, John F. Trepanowski, Liana C. Del Gobbo, Michelle E. Hauser, Joseph Rigdon, John P. A. Ioannidis, Manisha Desai, Abby C. King. Effect of Low-Fat vs Low-Carbohydrate Diet on 12-Month Weight Loss in Overweight Adults and the Association With Genotype Pattern or Insulin Secretion: The DIETFITS Randomized Clinical Trial. JAMA, 2018; 319 (7): 667-679 DOI: 10.1001/jama.2018.0245 
  2. Centers for Disease Control and Prevention: Overweight and Obesity https://www.cdc.gov/obesity/resources/strategies-guidelines.html 

Transcript

Dr. Frank Domino:
Carmen is a 38-year-old female from Puerto Rico, who comes in today for a follow-up of her obesity. She has been overweight, or obese, since her preteen years. And her BMI, which was 38 at the last visit, has now risen to 40. Her diet consists of rice and root vegetables. Carmen was told by a friend she might benefit from the South Beach Diet and wonders if it would work for her. Her friend told her she lost 10 lbs eating protein all day and eliminating all carbohydrates. Is this a good idea for Carmen?

Hi, this is Frank Domino, at the University of Massachusetts Medical School. And joining me today is Ken Peterson, Nurse Practitioner and Assistant Professor in the Graduate School of Nursing at the University of Massachusetts Medical School. Thanks for coming, Ken.

Kenneth Peterson:
Thank you, Frank, for inviting me.

Dr. Domino:
So, Carmen's like a lot of our patients. What's the best evidence out there for managing our patients who have weight issues, and in particular, those who are obese?

Kenneth Peterson:
It's becoming a bit confusing. We have lots of evidence and what we've thought has been really good evidence around particular diets and exercise and, if you think about it, over the past 10 years or so, we've had lots of information on diets that follow particular trends, for example, high fat diets, low fat diets, high protein diets, grapefruit diets. A variety of things. And what's interesting is, we just learned about a diet analysis essentially, or some research on diet, from a publication in JAMA. Some researchers who ran a very strong RCT around looking at the effect of low fats versus low carbohydrate diets over a good period of time with some great statistical power. And I think that's what I'd like us to talk a little bit about today.

Dr. Domino:
Okay, great. Well, you did mention the trends we've seen with diets, from low fat, to low carb, to now fastings, a variety of sorts. What did this diet fits, randomized controlled trial tell us?

Kenneth Peterson:
So, this diet... This research told us that there's really no one diet that best fits individuals. That I think we have to think about things a bit differently and encourage our patients to eat healthy and nutritious foods. This is ultimately what we can do with this research.

Dr. Domino:
Ken, why don't you tell me how they ran this randomized controlled trial? What did they study? And how did they employ the intervention?

Kenneth Peterson:
So, this particular study looked at a group of 609 individuals and randomized individuals into two groups. One was the healthy low fat group and they had 305 subjects, and then the other group was the healthy low carb group, at 304. They randomized folks into these two groups and the intervention employed were small group sessions that focused on behavior modifications, trying to get these individuals to diets that were lowest in fats and carbohydrates. And they looked at these individuals over a period of time and actually ran these small group sessions over that time to help them sustain the work of these diets.

Dr. Domino:

So, it sounds like they've divided this group into two. One group got the low fat diet, healthy low fat diet, and the other were counseled on the healthy low carb diet. And did they meet with them once a month, or how frequently did they meet them?

Kenneth Peterson:
They met with them regularly. There was some initial emphasis to get them to really lower fat and carbohydrate intake over the first eight weeks of the study and then at intervals over the next several months, they had folks balance out their fat intake and their carbohydrate intake, so that they felt comfortable and were able to sustain those particular levels. Ultimately trying to keep the diets lower in fat and lower in carb.

Dr. Domino:
Okay, and it also sounded like they followed some physiologic markers. What did they do with regards to their specific genotype?

Kenneth Peterson:
So, there has been research that supports this idea that a patient's, or individual's, genotype supports a particular diet, whether it's low fat, or low carb, and there's actually been some good evidence. There's also been some evidence supporting this notion of insulin levels and insulin secretions, and so you would think in the context of diabetic patients, for example, they should have a low carbohydrate diet. So this study looked at the outcome of weight change, and then looked at the interaction of genotype and insulin secretions in relationship to the weight loss.

Dr. Domino:
Well, that makes good logical sense but now tell us, what did the study find?

Kenneth Peterson:
So, it was interesting, the study which was... As I mentioned earlier, was very well powered with the number of subjects, found that there was no real statistical significance in terms of weight change. Both groups lost about 13 pounds or so and in terms of the interactions of the genotype and the insulin secretion, there was no statistical evidence supporting that either in relationship to weight loss.

Dr. Domino:
Wow! So it didn't matter what their genotype was, both groups effectively lost about the same amount of weight over 12 months, around 13 pounds, and had the same insulin response to that weight loss. Well, that's terrific, it certainly makes it easier to counsel patients without having to order specific tests, or worry that one intervention might work for one subset of people and one intervention might work for another. How can we use this study in the course of our clinical practice?

Kenneth Peterson:
So this study is great. I think it helps us to realize that we need to simplify our approach. We know that helping people lose weight has been challenging, and it's very challenging for both patients and for providers in terms of the approach that we take. I think one approach that a lot of people take gets to fairly complicated recommendations about diet and exercise, and this study helps us to realize that it's probably not that difficult, that we should be simplifying things and we should be getting our patients to eat healthy, wholesome, nutritious foods and just concentrate on foods that they like, eliminating processed foods and trying to follow through with recommendations of exercise as well.

Dr. Domino:
That's a fairly big change. I think, in at least in the last 10, 15 years, a great deal of the focus has been on helping folks cut back on especially simple carbohydrates and processed foods. And now this study says, if someone possibly prefers to go with a healthy low fat diet, they can still eat a fair amount of carbs, as long as they keep up and keep on the healthy side. Does that sound about right?

Kenneth Peterson:
It does, exactly. And I think what this study probably is showing is that over this 12 month period of the study, that regardless of which group you're in, that you probably had lower calorie burden and you basically got yourself into a deficit, which is the best way to lose weight, essentially. Yes.

Dr. Domino:
Well, that sounds great. It certainly makes it much easier to counsel patients and help them do the things they like to do, but maybe with a healthier twist. Well, Ken, thank you for bringing this to our attention today.

Kenneth Peterson:

You're welcome.

Dr. Domino:

Practice pointer. Helping patients lose weight involves identifying what foods they like, not necessarily eating just a low carb or a low fat diet. If patients prefer carbohydrates, help them identify healthy carbohydrates, limit their fat intake and get them exercising. Likewise, if they prefer fats, help them identify healthy fats, limit their carbohydrate and keep them going. Join us next time when we discuss the effect of technology on sleep disorders in children and adolescents.