To conclude this brief series on our new exhaustive review of the putative health benefits of long-term weight-loss maintenance, published in Annual Reviews of Nutrition, here is the summary paragraph of our findings:
“Obesity is well recognized as a risk factor for a wide range of health issues affecting virtually every organ system. There is now considerable evidence that intentional weight loss is associated with clinically relevant benefits for the majority of these health issues. However, the degree of weight loss that must be achieved and sustained to reap these benefits varies widely between comorbidities. Downsides of weight loss that is too rapid and/or extreme may occur, as in the increased risk of gallbladder disease, the presence of excess residual skin, or deterioration in liver histology. Uncertainty also remains about the potential benefit or harm of intentional weight loss on patients presenting with some chronic diseases and on overall mortality. Clearly, well- controlled prospective studies are needed to better understand the natural history of obesity and the impact of weight-management interventions on morbidity, quality of life, and mortality in people living with obesity.”
The is much left to be done and answering some of these questions will become progressively easier as better treatments for obesity become available.
While the health benefits associated with intentional weight loss for some complications of obesity (such as elevated lipids and diabetes) are well documented, high-quality studies to back many other potential health benefits are harder to find.
Just how well (or poorly) the putative health benefits of long-term intentional weight loss are documented for each of the many conditions associated with obesity, is now detailed in a comprehensive review of the literature that we just published in the Annual Reviews of Nutrition.
The 40 page long review, which includes almost 250 relevant publications, supports the following main findings:
- Defining and assessing clinically relevant obesity and weight change are challenging tasks. In a given individual, there is often little relationship between the magnitude of obesity and measures of health.
- Despite its modest effect on long-term weight loss, behavioral modifications thatimprove eating behaviors and increase physical activity constitute a cornerstone for integral and sustainable weight management.
- Intentional weight loss is associated with a clinically relevant reduction in blood pressure, improvement in cardiac function, and reduction in cardiovascular events. The duration and magnitude of weight change required to achieve a significant benefit are still unclear.
- In individuals with impaired glucose metabolism at any stage, intentional weight loss achieved by any means is associated with a proportional reduction in T2DM prevalence, severity, and progression.
- Intentional weight loss is consistently associated with a clinically relevant reduction in triglycerides and increase in HDL cholesterol. The effects of weight loss on LDL cholesterol are less consistent.
- Overall, nonalcoholic fatty liver disease is commonly associated with excess weight and can show marked improvement with behavioral, pharmacological, and/or surgical weight loss. Very rapid weight loss, however, may worsen liver histology in some patients. Simi- larly, gallbladder disease is not only common in patients presenting with obesity but also highly prevalent after intentional weight loss.
- Obesity is widely recognized as a key modifiable risk factor for osteoarthritis, with sig- nificant improvements in pain and function reported with weight loss.
- Obstructive sleep apnea and obesity hypoventilation syndrome tend to improve with moderate weight loss; however, complete resolution is not common and is related to very significant weight loss.
- Asthma and COPD are clearly associated with obesity. Sustained weight loss seems to be associated with a significant improvement in asthma symptoms. Data for COPD are rather limited.
- Pregnant women who under go bariatric surgery seem to be less likely to present obstetric complications such as gestational diabetes, preeclampsia, and macrosomia.
- Data on weight loss and suicide are controversial. Caution may be in order when con- sidering bariatric surgery in patients with a history of suicide ideation or attempt.
- Data suggest that long-term weight loss is associated with an improvement in health- related quality of life. The amount of weight loss required to achieve a significant change, however, remains controversial.
However, there are many other issues where putative benefits of intentional weight loss remain even less clear than with the above.
For many conditions we will likely not know the long-term benefits of obesity treatments till better treatments become available and are tested in affected individuals.
If you are planning to attend the 4th Canadian Obesity Summit in Toronto next week (and anyone else, who is interested), you can now download the program app on your mobile, tablet, laptop, desktop, eReader, or anywhere else – the app works on all major platforms and operating systems, even works offline.
You can access and download the app here.
(To watch a brief video on how to install this app on your device click here)
You can then create an individual profile (including photo) and a personalised day-by-day schedule.
Obviously, you can also search by speakers, topics, categories, and other criteria.
Hoping to see you at the Summit next week – have a great weekend!
The recently released Canadian Practice Guidelines on the prevention and management of overweight and obesity in children and youth released by the Canadian Task Force on Preventive Health Care (CMAJ 2015), rightly recommended that surgery not be routinely offered to children or youth who are overweight or obese.
Nevertheless, there is increasing evidence that some of these kids, especially those with severe obesity, may well require rather drastic treatments that go well beyond the current clinical practice of doing almost nothing.
Just how ill kids can be before they are generally considered potential candidates for bariatric surgery is evident from a study by Marc Michalsky and colleagues, who just published the baseline characteristics of participants in the Teen Longitudinal Assessment of Bariatric Surgery (Teen-LABS) Study, a prospective cohort study following patients undergoing bariatric surgery at five adolescent weight-loss surgery centers in the United States (JAMA Pediatrics).
While the mean age of participants was 17 with a median body mass index of 50, the prevalence of cardiovascular risk factors was remarkable: fasting hyperinsulinemia (74%), elevated hsCRP (75%), dyslipidemia (50%), elevated blood pressure (49%), impaired fasting glucose levels (26%), and diabetes mellitus (14%).
Not reported in this paper are the many non-cardiovascular problems raging from psychiatric issues to sleep apnea and muskuloskeletal problems, that often dramatically affect the life of these kids.
While surgery certainly appears rather drastic, the fact that these kids are undergoing surgery is merely an indicator of the fact that we don’t have effective medical treatments for this patient population, which would likely require a combination of behavioural interventions and polypharmacy to achieve anything close to the current weight-loss success of bariatric surgery.
That this cannot be the ultimate answer to obesity management (whether for kids or adults), is evident from the rising number of kids and adults presenting with ever-higher BMI’s and related comorbidity – not all of these can or will want surgery.
Thus, while current anti-obesity medications cannot compete with the magnitude of weight-loss generally seen with surgery, medications together with behavioural interventions may well play a role in helping prevent progressive weight gain in earlier stages of the disease.
Unfortunately, I am not aware of any studies that have explored the use of medications in kids to stabilize weight in order to avoid surgery. This would, in my opinion, be a very worthwhile use of such medications.
Given that virtually every risk-factor guideline (from hypertension to diabetes) recommends “weight-loss” as “first-line” treatment, to many this may seem a rather stupid question, but in reality, there is in fact almost no high-qulaity evidence to show that intentional (non-surgical) weight loss actually reduces mortality.
This may well be simply because randomised controlled studies on intentional weight loss have either never been long enough, big enough, or able to sustain large enough differences in body weight between the interventions arms.
Nevertheless, now a meta-analysis by Stephen Kritchevsky and colleagues from the Wake Forest School of Medicine, published in PLOS one, suggests that being randomised to the intervention arm in a weight-loss study may reduce mortality by 15%.
The researchers identified 15 randomised controlled trials of behavioural interventions for weight loss of at least 18 months duration, of which 12 reported at least one death in either of the intervention arms.
These studies included 17,186 participants (53% female, mean age 52 years, mean BMI range 30–46 kg/m2 ) with follow-up times ranging from 18 months to 12.6 years (mean: 27 months), and an average weight loss of 5.5±4.0 kg.
Based on a total of 264 deaths in weight loss groups compared to 310 in non-weight loss groups, the authors calculated a 15% lower all-cause mortality risk (RR = 0.85; 95% CI: 0.73–1.00) in the weight-loss group.
Thus, the authors conclude that being randomized to the weight-loss arm in a behavioural weight-loss study may indeed reduce mortality risk.
However, as readers may realise, this study certainly does not “prove” that it is the actual weight loss that mediates these effects. After all, to achieve and sustain weight-loss through behavioural interventions, participants would have had to change their diet and activity levels to a greater extent that those in the control group. Thus it is very possible that the difference in mortality between the groups could well have been due to changes in health behaviours rather than due to the actual weight loss.
Nevertheless, the findings are reassuring in that they at least do not show an increase in mortality, something that people have feared may happen with intentional weight loss, especially in older individuals.
I guess the most we can conclude from this study is that being lucky enough to be randomised into the “weight-loss arm” of a behavioural weight-loss RCT may just help reduce your mortality risk.