This study is to our knowledge the first designed specifically to examine the effects of an intensive lifestyle intervention on weight loss, abdominal fat, hepatic steatosis, and other cardiometabolic risk factors in persons with severe obesity. Our results indicate that this non-surgical approach can be an effective treatment for severe obesity. The approximately 10% weight loss achieved is similar to that reported for overweight and class I obesity.22,23
Moreover, nearly 30% of participants achieved more than 10% weight loss, and 10% of participants achieved greater than 20% weight loss at 12 months. Adherence to the intervention by these severely obese participants was the same as that previously reported in overweight and obese participants.15,24
This is in accord with other studies that have reported significant diet-induced weight loss in severe obesity.11,25,26
Thus, our results directly counter the dogma that these severely obese individuals do not respond to life-style intervention. In addition, despite the slightly lower weight loss in African Americans, the interventions were effective in white as well as African American individuals, the latter of whom are at particular risk for type 2 diabetes and cardiovascular disease.27,28
Our intent is not to compare our results with those obtained with bariatric surgery, nor do we recommend that intensive lifestyle modification replace bariatric surgery. To the contrary, it is quite clear that bariatric surgery should continue to play an important role in the treatment of severe obesity. It should be pointed out, however, that many studies comparing surgery with conventional therapy for weight loss have implied that lifestyle intervention is synonymous with conventional therapy. We agree that conventional therapy is generally inadequate to treat severe obesity. In one of the few clinical trials focusing on the treatment of severe obesity, Ryan et al12
reported that severely obese adults randomized to an intensive medical weight loss program in a primary care setting lost a significant amount of weight compared with those receiving usual care; in that study, 21% of participants lost 10% or more of their weight. As is the case with many weight loss trials, however, the primary limitation of that study was that retention rates were relatively low. The more frequent and structured intervention contact in our study likely contributed to the relatively high adherence and retention and thus the degree of weight loss.
The addition of physical activity, regardless of whether initiated early in the program or delayed, promoted greater weight loss. This effect was statistically significant for the group×time interaction for body weight from baseline to 6 months, although the group×time interaction did not reach statistical significance when the data were analyzed as calculated weight change. Although weight loss was not statistically different between groups after physical activity had begun in the delayed-activity group, physical activity may have contributed to the ability to sustain weight loss from 6 to 12 months.
Our results are consistent with studies in overweight and class I obese participants reporting that the addition of physical activity modestly but significantly induces greater weight loss and is important to maintain weight loss.29
Moreover, these severely obese adults did not present with any particular physical limitations that precluded them from initiating a physical activity program at the onset of the weight loss intervention. This suggests that physical activity could also play an important role in the long-term maintenance of weight loss following bariatric surgery, which is in accord with previous associations between physical activity and degree of weight loss following bariatric surgery.30
Additional studies are clearly needed, however, to examine the long-term effects of physical activity on weight loss in severe obesity.
Another clinically relevant finding was the significant reduction in abdominal fat and hepatic steatosis. Abdominal fat assessed by imaging methods or by surrogate waist circumference is regarded as more strongly associated with type 2 diabetes and cardiovascular disease risk than is generalized obesity.31–34
Moreover, a large prospective cohort analysis revealed that higher waist circumference strongly predicts mortality.35
Hepatic steatosis is strongly associated with insulin resistance36,37
and a higher risk of cardiovascular disease.38
Although this lifestyle intervention did not achieve the degree of weight loss typically observed following bariatric surgery, this magnitude of weight loss was associated with significant improvements in insulin resistance, blood pressure, and levels of plasma triglycerides. Moreover, the greater reductions in waist circumference and degree of hepatic steatosis with the addition of physical activity indicate that the benefits of physical activity extend beyond effects on generalized obesity.
Our study also has several limitations. Participants were mostly women, and although groups were randomized according to sex, it is difficult to determine sex-specific responses. Additional studies should examine the effects of sustained intensive lifestyle intervention on long-term weight loss among severely obese persons and on the use of antihypertensive and lipid-lowering medications.
In conclusion, intensive lifestyle interventions using a behavior-based approach can result in clinically significant and meaningful weight loss and improvements in cardiometabolic risk factors in severely obese persons. It is also clear that physical activity should be incorporated early in any dietary restriction approach to induce weight loss and to reduce hepatic steatosis and abdominal fat. Our data make a strong case that serious consideration should be given by health care systems to incorporating more intensive lifestyle interventions similar to those used in our study. Additional studies are clearly needed to determine long-term efficacy and cost-effectiveness of such approaches.