The dramatic results of a highly publicized Tulane University study supports a low carb diet as a more effective route to weight loss than a low fat one.
Participants in the study were obese people from Louisiana. Over half were African American, and 90% were women. One group was put on a low-carb diet for about a year; the other group went on a low-fat diet for the same amount of time. Overall, 80% of the subjects completed the trial.
Although both groups attained positive results, the study showed a significant difference in health indicators between the low carb and the low fat groups.
|Average Pounds Lost||Fat Mass Lost||Lean Mass Gained|
|LOW-CARB GROUP||11.7 lbs||1.2%||1.3%|
|LOW-FAT GROUP||3.9 lbs||0.3%||0.4%|
Some concerns have been raised about how the trial was conducted, especially because adherence to the diet was reported by the participants themselves, and not strictly controlled by researchers.
The low-carb group was instructed to limit daily carbs to under 40 grams carbs daily – about the amount of carbs in two slices of bread. They were not to change their activity levels, and they received low carb meal replacement shake or bars as well as dietary counseling.
Over the same year, the low-fat group’s mission was to reduce daily dietary fat to less than 30 percent of daily calories. Like the low carb group, they also did not change activity levels, and were given low-fat meal replacement shake or bars and dietary counseling.
Neither of the groups actually reached their carb or fat reduction goals, although participants in both groups did make major changes in their diets. For example, near the end of the trial, the average carb intake among the low carb group was nearly 130 g per day, about half of their self-reported pre-trial average daily carb intake. Interestingly, the daily protein intake of this group rose during the 12 months, from 18 percent of calories to 25 percent.
Participants in the low-fat group had begun the study with a self reported diet in which 35 percent of total calories was fat. This figure went down to 30% over the length of the trial – not a particularly low-fat diet. The low-fat group reduced their daily calorie intake by about 500 calories a day, and with it their fat intake also went down by 30 grams a day. However, over the period of the trial, the low fat group’s carb intake increased to over 50 percent of total calories.
Ultimately the study did not end up providing evidence comparing low fat to low carb diets. Instead, the results do tell us that when it comes to weight loss, reducing dietary carbs makes a bigger difference than reducing fat in our diets.
Also reducing carbs for a year can result in better heart health than reducing fats. At the end of the trial, the low-carb group (whose diets included surprisingly high saturated fat content) demonstrated better results related to reduced risk for heart disease than did the low-fat group. The low carb group had a higher HDL to total cholesterol ratio, lower triglycerides, slightly better reduction in LDL, and a greater decrease in C-reactive protein, along with an overall lower calculated heart disease risk score.
The study also highlighted the value of increasing protein intake in improving weight loss, even for people on the standard American diet. Finally, and predictably, reducing calories is still the most important feature of a weight loss plan.