A new research study presented additional evidence of the benefits of a lower-carb approach to diet. The study was published in the Annals of Internal Medicine and financially supported by the National Institutes of Health.(1) It compared a calorie-controlled low-fat diet, against a low-carb diet in which participants were allowed to eat as much protein and fat as they wanted, over a two-year period. The bottom line finding was that both approaches led to the same weight loss over two years, but the low-carb diet led to much greater levels of health-promoting HDL cholesterol. Though this is the summary that’s made most of the news stories, there was additional, valuable information revealed in the study.
The study group consisted of overweight individuals who were put into two different groups. The first group (low-fat group) was instructed to eat a diet consisting of 1200-1500 calories per day for women, and 1500-1800 calories per day for men. Of the total calories, 55% were to come from carbohydrate, 30% from fat and 15% from protein. Interestingly, it was only this group was instructed to maintain a specific calorie level.
The second group was instructed to follow a specific Atkins-diet protocol. In the first three months, they were to keep carbohydrate content below 20 grams per day from fibrous vegetables, while freely eating as much protein and fat as they wanted to. After the first three months, they gradually increased carbohydrate intake. Each week after the first twelve weeks, they were told to add an additional five grams of carbohydrate to their daily intake.
During the first twenty weeks (~five months), both groups received in-person, group support. Exercise and multivitamin recommendations were the same for both groups.
Not surprisingly, the groups lost their greatest amount of weight at the six-month mark, shortly after the group support program ended. This is important in that for many overweight individuals, without the support and accountability of a group or one-on-one program, they easily get off-track with their nutrition plan. From the six-month mark to the end of two years, weight crept back on in both groups to the point where, at the end of the study, both groups had lost 7% of their body weight from where they started, which averaged 15 pounds.
Dietary adherence is one of the most challenging aspects of studying nutrition. Without cooking meals every day for individuals, it’s nearly impossible to ensure they follow the prescribed plan. In many studies, the low-fat group tends to maintain a closer diet to what is recommended than the low-carb groups do. This is because the “low-fat” approach is not dramatically different than the Standard American Diet (SAD), where as the low-carb plan is quite different than most people in today’s society eat. From a weight loss perspective, a key point is that the low-fat group had to count calories to lose the weight, whereas the low-carb group simply had to limit carbohydrate intake. It would have been even more interesting if, over the two years, all foods would have been prepared for the low-carb group to ensure they stuck to the plan. Of course, it isn’t feasible for studies such as these to have that much control over food intake for such a long period of time.
Although LDL cholesterol was lower at Month 3 and Month 6 in the low-fat group, VLDL (small, dense LDL), which is the real “bad” cholesterol was lower in the low-carb group. A common misconception about low-carb diets is that they raise LDL cholesterol, but it is the large, fluffy LDL particles that usually rise on a low-carb diet, which does not present the health risk that VLDL cholesterol does. Excess carbohydrates tend to cause a rise in VLDL cholesterol. HDL cholesterol, a known protector against heart disease, often decreases with a low-fat diet. Consumption of fat, especially saturated fat, helps increase HDL cholesterol.(2) The recent study again confirmed this finding.
During the first year of the study, triglyceride levels fell dramatically more in the low-carb group than in the low-fat group. High triglyceride levels are another known indicator of heart disease risk. In the second half of the study, the second year, the difference in triglyceride levels was less significant. The change in triglycerides in the second half of the study was likely due to an increase in carbohydrate intake, which is common among those who participate in a low-carb study without regular support and accountability.
Bone mineral density was measured over the two-year period as well. Low-carb diets have a reputation for decreasing bone mineral density because of their higher protein intakes, although research has not supported that reputation.(3) This study showed that the low-carb approach was not detrimental to bone density. Generally, higher-protein diets can increase the body’s acid load, which requires more minerals to offset the acids. Consuming sufficient vegetables can offset any potential risks for decreasing bone density when consuming protein, and some studies show that higher-protein diets are better for maintaining bone density with aging.
We can glean a few important points from this study, which have been mentioned before. First, changing dietary habits is NOT easy. We live in a society where processed foods available everywhere. Without support, the chance of long-term success is greatly diminished. Until one’s life is completely changed, and they can’t think of going back to the old way of eating, it’s critical to find a support group. Support can be in-person, such as programs like EAT or TEAM. You may also find the support and encouragement you need through an online community. Participating in discussion forums and tracking what you eat can be great ways of finding motivation and accountability.
Second, evidence continues to mount which shows the positive outcomes from a reduced-carbohydrate diet for many people. Most peoples’ lifestyles are not active enough to justify the high amounts of carbohydrates we consume on a daily basis. The challenge, of course, is making the right decisions and avoiding the convenience foods we’re faced with each day. This goes back to the first point of connecting with a support group and staying connected with like-minded people.
Finally, lower-carbohydrate diets and higher-protein diets tend to go hand in hand. There is some debate as to which macronutrient plays a more significant role in weight management. Those who make protein intake a priority at each meal tend to eat less carbohydrates and less food in general. For some people, it may be easier to think of changing their nutritional habits by increasing the intake of vegetables and protein rather than reducing carbohydrates. In the end, less carbohydrate and more healthy fat and protein should help you get to your weight-management goals easier.
- Foster G, Wyatt H, Hill J, Makris A et al. Weight and Metabolic Outcomes After 2 Years on a Low-Carbohydrate Versus Low-Fat Diet. Ann Intern Med. 2010;153:147-157
- Siri-Tarino P Sun Q, Hu F, Krauss R. Meta-analysis of prospective cohort studies evaluating the association of saturated fat with cardiovascular disease. Am J Clin Nutr. 2010;91:525-546
- Darling A, Millward DJ, Torgerson DJ, Hewitt C, Lanham-New S. Dietary protein and bone health: a systematic review and meta-analysis. Am J Clin Nutr. 2009;90(6):1674-1692
This article is not intended for the treatment or prevention of disease, nor as a substitute for medical treatment, nor as an alternative to medical advice. Use of recommendations in this and other articles is at the choice and risk of the reader.