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Wednesday
Aug042010

Low-Carb Tops Low-Fat...Again

Written by Tom Nikkola - Director of Nutrition & Weight Management

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.

Study Design

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.

Study Findings

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.

Summary

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.

References:

  1. 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
  2. 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
  3. 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.

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Reader Comments (1)

There is always a study to prove one "diet" is better than another. Some of the longest lived and healthiest people in the world live high carbohydrate starch based diets with little to no animal protein. The China Study by T. Colin Campbell PhD shows ample scientific proof for this. His study was 25 years long and not just 2. Dr. McDougal's work also shows similar conclusions. The difference is that these diets contain minimal to no processed foods or dairy and very little protein from animal sources. A healthy diet cannot simply be limited to the low-carb or low-fat categories. Nutrition is not compartmentalized this way in our bodies. The entirety of the diet and the quality of all the foods eaten play a synergistic role in determining health. Not to mention that we are not created equal in regards to our nutritional requirements, and a diet that is beneficial for one may be harmful for another. Men and women certainly have different requirements. And in regard to the possibility of a cardiovascular event at lower cholesterol levels, a person would be hard pressed to find one for a person whose cholesterol is below 150. Of course if that level is a result of starvation or living on nothing but refined sugars health complications are sure to be the result.
The comment about humans not being active enough to sustain the amount of carbohydrates we eat daily is certainly true but our bodies were designed to be active and to use quality carbohydrates as our primary fuel. Top level athlete do not thrive on a low-carb diet. Their bodies reach performance peaks on carbs. Even strength athlete ingest carbs before their activities for extra energy even though they require more protein in their diets. Many top level athletes are whole food vegans or raw foodists. They have amazing health and weight control. Maybe the answer is to get more activity instead of changing the diet to accommodate a more sedentary life.

All I really mean to get across is that there is a bigger picture to diet and health than the great low-carb low-fat debate. fi you switch from a heavily processed diet to a whole foods diet with greater consumption of nutritional powerhouses like dark green leafy vegetables, there is usually only improvement. It may be that the results of the low-carb diet are not so much from animal protein and fat consumption but from the fact that it forces you to reduce the amount of processed foods that are eaten. After all most processed foods are laden with refined carbohydrates, especially sugar. Similarly the low-fat diet excludes all the highly processed fatty foods consumed in the standard american diet like mayo, cheese containing products, and chips. However these people may consume far to many carbohydrates from grains and refined wheat flour and not enough from vegetables or higher quality grains such as quinoa and millet. But the point is you have to see the diet in its entirety before you can draw conclusions as to what makes it better for you or successful in weight management.

So do a little research and study many perspectives on diet and nutrition. You'll find they all are not that difference and many share many common themes and principles. See the whole picture.

April 11, 2012 | Unregistered CommenterCloeyhds

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