The media has been buzzing over the low-carbohydrate vs. low-fat headline that stemmed from a recent study in the Annals of Internal Medicine, so as discussed in earlier posts, let’s read beyond the headlines.
The randomized, parallel group study looked at a low-carbohydrate vs. low-fat diet on body weight and CVD risk factors. Some positive attributes of this study were that it included a fair amount of black participants and had a sample size of 145 obese but otherwise healthy individuals (although skewed, with 88% being women).
Participants in the study received a handbook with instructions and recipes, a meal replacement [low-carbohydrate or low-fat, based on assigned group], and counseling sessions from a registered dietitian (individual for the first four weeks, every other week group counseling for the next 5 months and monthly during the last 6 months). No calorie limit was set for the groups, and participants were encouraged not to change physical activity during the intervention. Emphasis was placed on fiber and types of fats (trans fats to be decreased and MUFAs increased) for both groups. Dietary recalls were used (one weekend/one week day) at baseline, 3, 6 and 12 months, and labs and anthropometrics were measured by trained staff using procedures set forth by AHA, NHLBI and CDC.
Results showed that energy intake dropped in both groups from baseline. Notable is that the low-carbohydrate group consistently reported consuming 100+ fewer calories than the low-fat group throughout the study. Interestingly, the low-carbohydrate group consumed optimal amounts of protein, 81-90 g protein daily, whereas the low-fat group dropped to 60-70 g protein daily. Both groups consumed inadequate intakes of fiber – about half of what was recommended for the study – but this matches typical intakes for Americans.
Weight loss was greater for the low-carbohydrate group and remained significant throughout the 12-month study. LDL-cholesterol and triglycerides decreased in both groups; HDL increased, and CRP decreased in the low carbohydrate group. In addition, 10-year Framingham risk decreased for the low-carbohydrate group.
Although the study has been criticized by some, it does add to the current body of evidence on low-carbohydrate diets. Unlike many of the previous low-carbohydrate studies, this trial looked at free-living individuals. Participants in both groups were able to make dietary changes that shifted macronutrient intake and reduced calories overall. Unfortunately, the paper did not report actual foods consumed, which would have been interesting. In addition, there were no apparent negatives with the low-carbohydrate diet on measured outcomes. Although no one study is perfect, the results of this present trial build on prior evidence that a reduced carbohydrate diet may be a feasible option for those wanting to improve their weight and health without the “fear of fat” dogma.