The principal finding of this study was that lifestyle interventions delivered in primary care settings helped patients achieve modest weight losses that were associated with improvements in cardiometabolic risk factors. Enhanced Brief LC, in which meal replacements or weight loss medications were used in conjunction with quarterly PCP visits and monthly brief lifestyle coaching, conferred the largest weight losses and generally the greatest improvements in cardiometabolic risk factors. The largest improvements were seen in markers of insulin resistance, as indicated by reduced fasting insulin levels and decrements in HOMA-IR. These benefits were sustained throughout the duration of the study. Significant changes also were observed in HDL cholesterol over time in the Enhanced Brief LC group.
All three interventions produced modest reductions in total and LDL cholesterol, triglycerides, and hs-CRP at one or more times during the trial. Net beneficial effects on lipids and inflammatory markers generally were maintained, despite some weight regain in all groups. In contrast, systolic and diastolic blood pressure were essentially unchanged in all groups.
Our findings of modest reductions in lipid parameters and minimal changes in blood pressure are similar to those reported in the POWER-Hopkins study, in which obese participants with at least one cardiovascular risk factor were randomly assigned to a self-directed control group or to one of two behavioral interventions. Weight-loss counseling was provided remotely (via phone, email, or web-based applications) or in-person, using group and individual sessions.14
Weight loss at month 24 in the two intervention groups (−4.6 and −5.1 kg, respectively) was similar to that observed in our Enhanced Brief LC participants. We note that baseline values for blood pressure and lipids were near normal in POWER-UP and POWER Hopkins, thus, limiting the capacity to assess the potential benefits of weight loss on these outcomes.
To better describe the associations between weight change and improvements in cardiometabolic risk factors, we also examined the effects of incremental categories of weight loss, irrespective of the treatment condition. Although it is generally accepted that weight loss ≥5% in obese individuals induces favorable changes in numerous CVD risk factors,1–5
we observed smaller changes in several metabolic parameters than others have previously described.3
In the Look AHEAD (Action for Health in Diabetes) study, weight loss of 5 to <10% (compared with ≤2%) was associated with increased odds of achieving clinically significant improvements in systolic and diastolic blood pressure, HbA1c
, glucose, triglycerides, LDL cholesterol, and HDL cholesterol.3
Larger weight losses (≥10%) were associated with greater benefits in all of these parameters, with the exception of LDL cholesterol. In contrast, we did not observe significant improvements in blood pressure, total cholesterol, LDL cholesterol, and fasting glucose with greater weight loss (i.e., ≥5% and ≥10%, compared with <5%) in the present study. Total and LDL cholesterol levels tended to improve with weight loss, but there were inconsistencies across graduated categories of weight change. (The lack of a dose-response relationship may have been attributable to the differential use of cholesterol medications in the four weight loss categories, but we were not able to confirm this hypothesis.) The Look AHEAD study included over 5,100 participants and was better powered to detect differences in cardiometabolic risk among categories of weight change. Moreover, as noted previously, POWER-UP participants had near-normal baseline values for many of the cardiometabolic variables examined.
Strengths of the present study include its diverse population, which is generally representative of primary care practices across the country and potentially makes our results generalizable to the broad population. The study also had a very high rate of adherence and follow-up over its 2-year duration, suggesting that it is possible to engage patients in behavioral weight loss programs delivered in primary care practice. Our investigation also had limitations, principally that it was not powered to detect significant differences between groups in cardiometabolic risk factors. (The study was powered on differences in weight loss.) Thus, our nonsignificant relationships between weight loss and improvements in blood pressure, glucose, and lipids should be interpreted with caution.
Despite these limitations, clinically meaningful improvements were observed in the present study in measures of insulin resistance, triglycerides, HDL cholesterol, and hs-CRP. These results reaffirm the important benefits of providing lifestyle counseling to appropriate patients to induce weight loss. The Enhanced Brief LC approach, developed in POWER-UP, provides a potentially valuable means of achieving clinically significant weight loss (≥5%) in primary care practice.