HEALTH NEWS

Study Title:

Dietary Weight Loss Improves Hardened Arteries

Study Abstract

Background—It is currently unknown whether dietary weight loss interventions can induce regression of carotid atherosclerosis.

Methods and Results—In a 2-year Dietary Intervention Randomized Controlled Trial–Carotid (DIRECT-Carotid) study, participants were randomized to low-fat, Mediterranean, or low-carbohydrate diets and were followed for changes in carotid artery intima-media thickness, measured with standard B-mode ultrasound, and carotid vessel wall volume (VWV), measured with carotid 3D ultrasound. Of 140 complete images of participants (aged 51 years; body mass index, 30 kg/m2; 88% men), higher baseline carotid VWV was associated with increased intima-media thickness, age, male sex, baseline weight, blood pressure, and insulin levels (P<0.05 for all). After 2 years of dietary intervention, we observed a significant 5% regression in mean carotid VWV (-58.1 mm3; 95% confidence interval, -81.0 to -35.1 mm3; P<0.001), with no differences in the low-fat, Mediterranean, or low-carbohydrate groups (-60.69 mm3, -37.69 mm3, -84.33 mm3, respectively; P=0.28). Mean change in intima-media thickness was -1.1% (P=0.18). A reduction in the ratio of apolipoprotein B100 to apolipoprotein A1 was observed in the low-carbohydrate compared with the low-fat group (P=0.001). Participants who exhibited carotid VWV regression (mean decrease, -128.0 mm3; 95% confidence interval, -148.1 to -107.9 mm3) compared with participants who exhibited progression (mean increase, +89.6 mm3; 95% confidence interval, +66.6 to +112.6 mm3) had achieved greater weight loss (-5.3 versus -3.2 kg; P=0.03), greater decreases in systolic blood pressure (-6.8 versus -1.1 mm Hg; P=0.009) and total homocysteine (-0.06 versus +1.44 μmol/L; P=0.04), and a higher increase of apolipoprotein A1 (+0.05 versus -0.00 g/L; P=0.06). In multivariate regression models, only the decrease in systolic blood pressure remained a significant independent modifiable predictor of subsequent greater regression in both carotid VWV (=0.23; P=0.01) and intima-media thickness (=0.28; P=0.008) levels.

Conclusions—Two-year weight loss diets can induce a significant regression of measurable carotid VWV. The effect is similar in low-fat, Mediterranean, or low-carbohydrate strategies and appears to be mediated mainly by the weight loss–induced decline in blood pressure.

From press release:

A low-carbohydrate diet, a low-fat diet and the Mediterranean diet were equally effective in helping obese people to reverse carotid atherosclerosis after losing moderate amounts of weight and improving their blood pressure, in a study reported in Circulation: Journal of the American Heart Association.

Researchers at Ben-Gurion University of the Negev, the Nuclear Research Center and Soroka Hospital in Israel investigated whether diet could reverse atherosclerosis, a slow, progressive condition in which the arteries thicken with plaque buildup, increasing risk of heart attacks and strokes. The research team compared the three diets among overweight participants, mostly men, who were at high risk for atherosclerosis.

After two years, researchers noted a significant 5 percent regression in average carotid vessel-wall volume and 1.1 percent decrease in carotid artery thickness.

Compared to participants who had increased carotid wall volume, those with decreases had other improvements:

•greater weight loss (11.7 pounds versus 7 pounds),
•decreased systolic blood pressure levels (6.8 mmHg versus 1.1 mmHg),
•improved homocysteine levels; and
•an increase in apolipoprotein A1 (Apo A1), the major component of "good" cholesterol.
The researchers said, beyond drug treatment, the data is some of the earliest showing the potential of diet as a lifestyle modification strategy to prevent atherosclerosis. The findings indicate that sustained, moderate weight loss -- not the macronutrient content of the different diets -- leads to improved cardiovascular health.

"Long-term adherence to weight-loss diets is effective for reversing carotid atherosclerosis as long as we stick to one of the current options of healthy diet strategy," said Iris Shai, R.D., Ph.D., study lead author and a nutrition epidemiologist at Ben-Gurion University of the Negev in Beer-Sheva, Israel. "This effect is more pronounced among mildly obese persons who lose more than 5.5 kilograms (12.1 lbs) of body weight and whose systolic blood pressure decreases by more than 7 mmHg. An increase in ApoA1 (HDL cholesterol apolipoprotein) and a decrease in total homocysteine blood levels are further associated with subsequent success in reversing carotid atherosclerosis."

Researchers studied 140 people (88 percent men, average age 51, average body mass index 30.4 kg/m2) from the Nuclear Research Center Negev who were randomly assigned to a low-carbohydrate, low-fat or Mediterranean diet as part of the Dietary Intervention Randomized Controlled Trial-Carotid (DIRECT-Carotid) study. Twenty-six percent of participants used lipid-lowering therapies, including 20 percent on statins, and nearly one-third of the group took blood pressure medication. They continued with their prescribed treatments throughout the study. Blood pressure was measured every three months, and blood samples to measure biomarkers such as homocysteine levels were collected after a 12-hour fast, at baseline, at six months and again at 24 months. Researchers used ultrasound to capture three-dimensional images of the carotid artery wall and to measure changes in arterial thickness at baseline and at the two-year follow-up.

Participants maintained food diaries and responded to diet questionnaires periodically throughout the study. While caloric deficits were similar among the three groups, intake of carbohydrates, fiber, dietary cholesterol and monounsaturated and saturated fats varied, depending on the type of diet. However, these variations in nutrient intake did not produce significant differences in the outcomes.

"The reduced caloric intake is probably the major determinant of weight loss, but the macronutrient content determines patients' satisfaction with the diet and the metabolic changes associated with the weight loss," said Yaakov Henkin, M.D., study co-author and a cardiologist at Soroka University Medical Center, Israel. "The importance of these results is in the understanding that over two years, changes in carotid atherosclerosis are more strongly predicted by diet-induced changes in blood pressure."

The study's findings are promising and could be applicable to other populations. But since few women were in the study, gender-specific effects remain unknown, researchers said.

American Heart Association diet and lifestyle recommendations underscore the importance of balancing calories with physical activity to achieve and maintain a healthy body weight and acknowledge that macronutrient content of the diet has little effect on energy balance with the exception of influencing diet satisfaction.

Study Information

Iris Shai, J. David Spence, Dan Schwarzfuchs, Yaakov Henkin, Grace Parraga, Assaf Rudich, Aaron Fenster, Christiane Mallett, Noah Liel-Cohen, Amir Tirosh, et al.
Dietary Intervention to Reverse Carotid Atherosclerosis
Circulation
2010 March
S. Daniel Abraham Center for Health and Nutrition, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel.