News Author: Shelley WoodCME Author: Charles Vega, MD, FAAFP
Because weight loss is so important to many of us, myself included, and, I am unable to provide a link to this article, (it is for members only), I decided to include the article, in its entirety for your review:
March 2, 2009 — It may be one of the most commonsense observations ever to be validated in a diet study: people lose weight if they eat fewer calories, regardless of where those calories come from . That's the upshot of a two-year study by Dr Frank Sacks (Harvard School of Public Health, Boston, MA) and colleagues, published in the February 26, 2009, issue of the New England Journal of Medicine.
After two years, 811 overweight adults randomized to one of four heart-healthy diets, each emphasizing different levels of fat, protein, and carbohydrates, showed similar degrees of weight loss. On average, patients lost 6 kg in six months, but gradually began to regain weight after 12 months, regardless of diet group.
According to Sacks, the research should help quell some of the debate — fostered by decades of research and fad diets — over what types of foods should be emphasized to produce weight loss.
"Research has looked at whether carbohydrate is more satiating than fat, or whether protein is more satiating than carbohydrates, or whether overeating fat puts more fat in the belly than overeating carbohydrates, etc," Sacks explained. "So what's concerned colleagues of mine on the nutrition guideline panels in the past is the possibility that if we say that a 40% fat diet is okay, that maybe that would lead to weight gain. But where this study is going to be helpful is in saying 40% fat, 20% fat, it doesn't matter. If people can maintain a calorie deficit no matter what type of diet they were on, they're going to lose weight."
Sacks, who is incoming chair of the American Heart Association's (AHA) Nutrition Committee, acknowledged that nutrition advice in the past has worried too much about fat in the diet. "I'm very concerned that we maintain the focus on calories and keep the focus off percent calories from fat," he said.
Another important, if unsurprising, finding from the study was that people who regularly attended counseling sessions over the two-year study were significantly more likely to lose weight.
The findings should remind physicians to hammer home the importance of losing weight. "Physicians really should, visit after visit, keep encouraging patients to eat a heart-healthy diet that they can stick with, that will help them lose weight, and try to get them involved in some kind of support group or to see a dietitian," Sacks said.
Commenting on the study for heartwire, Dr Robert Eckel (University of Colorado Health Sciences Center, Denver) said he wasn't surprised by the study findings. "I think you can lose weight in a number of different ways, and this study simply affirms that people who are successful are the people who adhere to a program. . . . Ownership, by the patient, of the weight-loss program is what proves successful, not the type of diet you chose."
The diets tested in the study included the same types of foods, but in different proportions, and were tailored to patients such that overall calorie consumption was reduced by approximately 750 calories per day, with each diet including a different macronutrient composition:
High-fat, average protein: 40% fat, 15% protein, 45% carbohydrate.
High-fat, high-protein: 40% fat, 25% protein, 35% carbohydrate.
Low-fat, average protein: 20% fat, 15% protein, 65% carbohydrate.
Low-fat, high-protein: 20% fat, 25% protein, 55% carbohydrate.
Participants were advised to exercise for at least 90 minutes per week, at a moderate level, and were offered counseling sessions every eight weeks, with group sessions held weekly or biweekly over the course of the study.
In all, 80% of subjects completed the trial, and 14% to 15% of subjects managed to lose at least 10% of their initial body weight. Subjects randomized to different groups reported similar degrees of satisfaction, hunger, and satiety. All the diets reduced risk factors for diabetes and cardiovascular disease at six months and two-year follow-up. At the two-year mark, the low-fat diets and the highest carbohydrate diet fared better than the high-fat diets and low-carb diet in terms of reducing low-density lipoprotein (LDL) cholesterol. By contrast, the lowest carbohydrate diet improved high-density lipoprotein (HDL)-cholesterol levels more than the highest carbohydrate diet. All of the diets produced slight improvements in blood pressure and decreased the number of patients with metabolic syndrome. All, with the exception of the highest carbohydrate diet, decreased fasting serum insulin levels.
External and Internal Motivators
An editorial accompanying Sacks et al's study applauds the duration of the study and the low dropout rate but takes a dimmer view of the weight loss achieved in the study and the ability of dieters to adhere to their diets over time . "Even these highly motivated, intelligent participants who were coached by expert professionals could not achieve the weight losses needed to reverse the obesity epidemic," Dr Martijn B Katan (VU University, Amsterdam, the Netherlands) writes. "The results would probably have been worse among poor, uneducated subjects. Evidently, individual treatment is powerless against an environment that offers so many high-calorie foods and labor-saving devices."
Sacks, speaking with heartwire, defended what he insisted was "clinically meaningful" weight loss in his study, emphasizing that many people achieved far greater losses than the average figure. Eckel, by contrast, was less sanguine, pointing out that an average weight loss of 3.5 kg at two years represents the best-case scenario, since real-life interventions rarely live up to the research setting.
Katan, however, argues that "like cholera, obesity may be a problem that cannot be solved by individual persons but that requires community action." He cites a French study that profoundly reduced obesity rates in children by having everyone in the town commit to getting children to eat less and move more, building sporting facilities and playgrounds, giving cooking workshops to families, creating walking itineraries, etc.
"It is an approach that deserves serious investigation, because the only effective alternative that we have at present for halting the obesity epidemic is large-scale gastric surgery," he writes.
In response, Sacks said simply that community wide changes won't absolve individual responsibility. "It's two factors. There's what each person puts into his or her mouth, and there's what's out there for people to choose to put in their mouths."
The National Heart, Lung, and Blood Institute and the General Clinical Research Center, National Institutes of Health, supported this study. Drs. Sacks and Katan have disclosed no relevant financial disclosures. A complete description of other disclosures for the other study authors is available in the original article.
Many adults have tried to lose weight through low-carbohydrate diets in the past several years, and there is some evidence that these diets may be more effective than traditional low-fat diets. In a study by Samaha and colleagues, which was published in the May 22, 2003, issue of the New England Journal of Medicine, a low-carbohydrate diet was associated with greater weight loss among a small cohort of obese patients with a high rate of diabetes or the metabolic syndrome. In addition, the low-carbohydrate diet was associated with superior results in serum triglyceride levels as well as insulin sensitivity among participants without diabetes. The 2 dietary interventions were similar with respect to their effects on levels of total and LDL cholesterol.The current study compares the efficacy of reduced-calorie diets featuring different macronutrient profiles.
Study participants were between the ages of 30 and 70 years and had a body mass index of 25 to 40 kg/m2. Individuals with diabetes, unstable cardiovascular disease, or who were judged to have poor motivation on screening interviews were excluded from study participation.
All study diets included 8% or less of the total calories from saturated fat, at least 20 g of fiber daily, and 150 mg or less of cholesterol per 1000 kcal. All diets restricted baseline individual participants' daily caloric intake by 750 kcal.
Participants were randomly assigned to 1 of 4 diet groups. The macronutrient contents of these diets were as follows:
20% fat, 15% protein, and 65% carbohydrates (low-fat, average-protein)
20% fat, 25% protein, and 55% carbohydrates (low-fat, high-protein)
40% fat, 15% protein, and 45% carbohydrates (high-fat, average-protein)
40% fat, 25% protein, and 35% carbohydrates (high-fat, high-protein)
Blinding was maintained by the use of similar foods for each diet.
Participants attended 3 group sessions for diet counseling per month during the first 6 months of the trial and then every 2 weeks from 6 months to 2 years. Individual counseling sessions were held every 8 weeks.
The goal for physical activity was 90 minutes per week for all participants.
The main outcome of the study was the change in body weight at 2 years, particularly comparing low-fat vs high-fat and low-protein vs high-protein diets. Researchers also followed waist circumference, participant satisfaction with diet, and laboratory markers of cardiovascular risk.
811 adults underwent randomization, and 80% completed the 2-year trial. Baseline characteristics were similar between the randomly assigned groups. The mean age of subjects was 51 years, 64% of the study cohort were women, and 79% were white. The mean body mass index was 33 kg/m2, and the mean waist circumference was 103 cm.
Weight loss at 2 years was similar in the 4 diet groups. Mean weight loss among participants in the 25% and 15% protein groups was 3.6 and 3.0 kg, respectively. The mean weight loss among subjects in both the low-fat and high-fat groups was 3.3 kg.
The level of carbohydrate in the diet did not significantly affect weight loss.
Waist circumference decreased by approximately 4 cm in all study groups.
Most weight loss occurred in the first 6 months of the trial. After 12 months, all groups, on average, slowly regained weight.
At 2 years, 14% to 15% of participants in each diet group had lost at least 10% of their baseline body weight.
Low-fat diets were associated with greater reductions in LDL cholesterol levels, whereas the lowest-carbohydrate diet promoted higher HDL cholesterol levels. All diets reduced fasting serum insulin levels, and blood pressure decreased modestly with all diet interventions.
Craving, fullness, and scores for hunger and diet satisfaction were similar among diet groups at 6 months and at 2 years.
Attendance at group sessions strongly predicted weight loss at 2 years.
7% of participants experienced severe adverse events. There was no difference among diet groups in the rate of severe adverse events.
Pearls for Practice
A previous study found that a low-carbohydrate diet was superior to a low-fat diet in weight loss, serum triglyceride levels, and insulin sensitivity. However, total cholesterol and LDL cholesterol levels were similar between groups.
In the current study, macronutrient concentrations of reduced-calorie diets did not significantly affect the amount of weight loss, the reduction in waist circumference, patient ratings of satisfaction with the diet, or the rate of severe adverse events. Greater attendance at group sessions predicted higher degrees of weight loss.
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March 13, 2009