Two-Year Study Shows Low-Carb Diet Effective For Weight Loss

LOW-CARBOHYDRATE DIET GROUP

(153 participants)
Carbohydrate intake was limited to 20 grams daily with unrestricted consumption of fat and protein during the first 12 weeks of the study. Permissible carbohydrates were limited to mainly low-glycemic index vegetables. Participants were encouraged to eat 4-5 small meals every few hours and to use butter, mayonnaise and vegetable oils instead of margarine and they were discouraged from trying to “do a low-fat version of the program as it will disrupt weight loss.” At the end of the first 12 weeks, study participants were allowed to increase their carbohydrate consumption by 5 grams daily each week in the form of more vegetables, some fruit, and even whole grains and dairy products until their weight became stabilized. The principles outlined in the all-time #1 bestselling low-carb diet book Dr. Atkins’ New Diet Revolution were encouraged, but the study participants were never provided with a copy of the book. They were told to watch their carbohydrate intake primarily while urged to consume foods that are “rich in fat and protein” to satiety. The behavioral modification implemented with this group was “to limit carbohydrate intake.”

LOW-FAT DIET GROUP

(154 participants)
Calories were limited to 1200-1500 daily for women and 1500-1800 daily for men with a fat/protein/carbohydrate ratio of 30/15/55. Study participants were strongly encouraged to keep their calorie intake reduced with a specific focus on cutting down on their fat consumption. The behavioral modification implemented with this group was “limiting overall energy intake.”

Participants in both groups received a 75-90 minute comprehensive, in-person group behavioral treatment led by a registered dietitian or psychologist with experience in weight control on a weekly basis for 20 weeks, then every other week for the next 20 weeks, and then ever other month for the rest of the study period where they were taught the SAFE method that includes Self-care, Adherence, Food records, and Exercise. Physical activity was identical for both groups in the form of walking beginning in week 4 with four sessions of 20 minutes each and then bumped up to four sessions of 50 minutes each by week 19. The study participants tracked their eating and exercise in a record book that was checked during their group sessions. A daily multivitamin was provided by the researchers to the study participants and encouraged for both groups.

What did Dr. Foster and his research team measure? Body weight was checked on each treatment visit where the participants wore light clothing and no shoes since this was the primary outcome they would be observing over the two-year period. However, additional health markers were checked out at 3, 6, 12, and 24 months, including:

BLOOD LIPIDS

Fasting blood samples were analyzed to look at HDL, triglycerides, VLDL, and LDL cholesterol. Precise measuring tools were used to obtain accurate lipid data.

BLOOD PRESSURE

After a 5-minute rest period, two blood pressure readings were taken separated by a 1-minute rest period. The average of the two readings was used to determine the blood pressure.

URINE KETONES

Ketone testing strips measured fasting ketone bodies in the urine and measured on a scale from negative to varying degrees of positive (trace, small, moderate, or large).

SYMPTOMS

A checklist of 26 symptoms were looked at to determine if there was none, mild, moderate, or severe in the study participants. Documentation of symptoms was labeled “absent” or “present” with a further breakdown in the latter group. The researchers note that most symptoms were listed as none or mild.

BONE MINERAL DENSITY AND BODY COMPOSITION

Bone mineral density and body fat composition was used at baseline and then again at 6, 12, and 24 months. Sophisticated full-body scanning instruments were used to determine these numbers.

All of the participants in the study were contacted via phone, mail, and e-mail for follow-up even if they dropped out of the study. And attrition rates were similar among both study groups. In the LOW-FAT DIET GROUP, the percentage of study participants who withdrew completely or had frequent absences from the scheduled meetings was 6% at 3 months, 12% at 6 months, 25% at 12 months, and 32% at 24 months. As for the LOW-CARBOHYDRATE DIET GROUP, attrition was slightly higher but statistically the same with 9% at 3 months, 16% at 6 months, 26% at 12 months, and 42% at 24 months. Although the study was funded by NIH (something low-carb science leaders like Dr. Mary C. Vernon has been pushing for years), they had no role in the “design, conduct or reporting of the study.”
What were the final results that the researchers found? Since body weight was the primary marker they wanted to observe, Dr. Foster and his team found that both groups lost a total of 11% of their starting weight at 6 and 12 months. However, by the end of the two-year study, the collective weight regain among both groups was 7%. One interesting bit of information they provided was the fact that there were “no statically significant differences in weight loss at any time point between the low-carbohydrate and low-fat diet groups.” But they did observe a “strong trend for greater weight loss” in the LOW-CARBOHYDRATE DIET GROUP before carbohydrate intake was elevated by 5 grams per day each week. In other words, as carbs were reintroduced into the diet, the differences in weight loss among the two groups became less pronounced until they were statistically the same.

Not surprisingly, urinary ketones were higher in the LOW-CARBOHYDRATE DIET GROUP at 3 months and 6 months as compared with the LOW-FAT DIET GROUP. But then something interesting happened–after 6 months, ketones bodies equalized among both groups as carbohydrate intake was increased gradually among the LOW-CARBOHYDRATE DIET GROUP which was the intent of the study. Yet it makes you wonder what would have happened had they kept carbohydrate intake at a level that would have been ketogenic over a longer period of time than 3-6 months. This was not observed in Dr. Foster’s study.

Regarding blood pressure, they saw similar decreases in systolic blood pressure among both study groups. Yet there were “significantly greater” reductions in diastolic pressure in the LOW-CARBOHYDRATE DIET GROUP at 3 and 6 months with a “strong trend” at 24 months. This is an observation that was previously recorded by researchers in a Duke University study published in the January 25, 2010 issue of Archives of Internal Medicine. On blood lipids, this was where the differences between the two groups became more pronounced, especially early on in the study.

The widest gap among the changes in this health marker were seen at 6 months when the LOW-FAT DIET GROUP saw a “significantly greater decrease” in LDL cholesterol levels, although this statistical change was negated by the time it was measured again at 12 and 24 months. Triglycerides decreased more among the LOW-CARBOHYDRATE DIET GROUP at 12 and 24 months and then became even at 12 and 24 months (again, as carbohydrate intake rose above ketogenic levels). Decreases in the VLDL cholesterol levels were “significantly greater” in the LOW-CARBOHYDRATE DIET GROUP at 3, 6, and 12 months, but not at 24 months (again, look at the ramping up of carbs among the study participants in that group). HDL cholesterol, commonly known as the “good” cholesterol, was predictably “significantly greater” in the LOW-CARBOHYDRATE DIET GROUP at every level measured ostensibly from the high-fat content of the foods they were consuming. This positive change in HDL cholesterol was the most notable difference between the two groups the researchers saw over the two-year period.

However, another key finding was with the bone mineral density. There were “no differences” between the two groups which is tantamount considering all the rumors that low-carb diets lead to osteoporosis and bone loss (this is ironic considering there is published data in 2006 showing a low-fat, low-calorie diet leads to bone loss). But the bone density was the same in both groups and the importance of this cannot be overemphasized since this is the first study of its kind to show that the bone mineral density change with low-carb diets is comparable to that of a low-fat diet. Another myth has been busted wide open with the published results of Dr. Foster’s study! Additionally, there was “no differences” in lean mass and fat mass between the two groups.

Symptoms from the LOW-CARBOHYDRATE DIET GROUP seemed to be “significantly greater” with reports of bad breath, constipation, and dry mouth during the first six months of the study which all could have been avoided with some simple measures included in most books and support groups for people following a low-carb diet. Curiously enough, although there have been headline-grabbing lawsuits purporting that a high-fat, low-carb diet caused heart disease in the past, there were “no serious cardiovascular events” that happened during this study. Dr. Foster noted that consuming a low-carb diet is not the heart health risk most medical professionals once feared.

A low carbohydrate diet is associated with favorable changes in cardiovascular disease risk factors at two years.

This coincides with Dr. Ronald Krauss’ January 2010 study vindicating saturated fat as a contributor in heart disease. And once again, another myth about high-fat, low-carb living has fallen by the wayside.

The conclusion of the study

The conclusion of the study zeroed in on two findings that Dr. Foster and his team of researchers considered most important. First, they contend that neither dietary fat nor carbohydrate intake were a factor in weight loss when they are combined with a comprehensive lifestyle intervention as was the case in this study. Second, since weight loss success over the period of the study was the same among both study groups, the only real lasting change that took place was in the HDL cholesterol of the low-carb dieters. They explained that the LOW-CARBOHYDRATE DIET GROUP “has greater beneficial long-term effects on HDL” than the LOW-FAT DIET GROUP did. This is a positive take-home message that validates previous research on low-carb diets.

Note that this study lasted two years which is considered a long-term research project. The complaint that low-carb nutrition has not been examined over an extended stretch can no longer be used by those who oppose carbohydrate-restriction (and yet again another myth bites the dust). Another important lesson from this study was the need for behavioral support in order to be successful. This is why follow-up with bariatric physicians or even a low-carb doctor for severely obese people is vital to attaining the desired results. The researchers readily admit that their purpose with this study was not to see the results of a long-term “Induction”-styled Atkins low-carb diet beyond 12 weeks. But the fact that even this low-potency low-carb diet did as well or better than the low-fat, low-calorie diet over a two-year period cannot be ignored. Just think if they had instituted a plan based on all the new science such as the runaway 2010 bestseller The New Atkins For A New You by high-fat, low-carb diet researchers Dr. Eric Westman, Dr. Jeff Volek, and Dr. Stephen Phinney what this improved, higher-potency low-carb diet could have done–no doubt there would have been upwards of 50-75 pounds of sustained weight loss annually with massive improvements in all the key health markers that were seen early on in the LOW-CARBOHYDRATE DIET GROUP. Now these findings will have to wait for the next low-carb study to come around for the next researcher to discover–although the trivial weight loss that has been shown in these studies can be discouraging to would-be low-carb dieters.

Dr. Foster gave low-carb diets the ultimate compliment after he analyzed the results of his study and offered up this final conclusion.

“These long-term data suggest that a low-carbohydrate approach is a viable option for obesity treatment for obese adults.”

That’s high praise indeed and interestingly enough there is already a physician-training program in place with CME accreditation teaching medical professionals from around the world the value of using carbohydrate-restricted diets with their metabolically-challenged patients. It’s from a group called Innovative Metabolic Solutions (IMS) led by Dr. Vernon, Dr. Westman, and New York Times science writer and bestselling author of Good Calories Bad Calories Gary Taubes. No doubt interest in such educational programs like this one offered by IMS will continue to grow as research from Dr. Foster and others continues to be published in major medical journals in the coming years.

If you appreciate the time and effort it took to put this quality low-carb diet research together over the past few years, then send Dr. Gary D. Foster an e-mail of thanks to [email protected]. Let him hear your gratitude for letting the results of the science he found guide him in his research. He’s a rare breed and deserves to be recognized for his stellar ethics and procedures with the publication of this fabulous low-carb study!

More Low Carb Articles by a former CarbSmart contributor