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.
In our exhaustive review of the potential health benefits of intentional long-term weight loss, published in Annual Reviews in Nutrition, I discussed in yesterday’s post, we also noted a number of issues that remain unresolved.
- The precise definition of success in terms of weight loss remains controversial, and the dogmatic assumption that prolonged periods of sustained weight loss (greater than 10 years) are more likely than shorter periods to have a beneficial effect on health out- comes has never been challenged.
- Some evidence suggests that intentional weight loss may lead to meaningful reductions in several conditions, such as COPD, and cancer risk with a short latency time, although data from randomized trials are not yet available to support this hypothesis.
- Future studies on the relationship between long-term weight loss and suicide are needed, especially in diverse populations, subgroups of patients, and those who engage in other long-term weight-loss strategies apart from the use of antiobesity medications and bariatric surgery. The potential relationship between failed weight-loss attempts and suicide ideation needs to be evaluated.
- There is ongoing controversy over the findings from epidemiological studies on the relationship between weight loss and mortality. Data from controlled studies in this regard are very limited.
Clearly, as we discussed at length here at the ongoing Canadian Obesity Network’s Obesity Research Summer School (Boot camp), much remains to be done for young researchers planning a career in this field.
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.
While there is evidence that weight loss can be beneficial for the treatment of polycystic ovary syndrome (PCOS), there are few studies that have actually done this in a controlled fashion – even fewer in adolescents.
To test the feasibility of a dietary intervention aimed at weight loss in adolescents, Wong and colleagues from Boston Children’s Hospital, conducted a study, the results of which are published in Pediatric Obesity.
The study was conducted in 19 overweight and obese adolescents with PCOS and not using hormonal contraceptives, who were randomised either to a a low-glycaemic load or a low-fat diet.
In the 16 participants who completed the study, reduction in body fat on either diet was minimal (between 1.2 and 2.2%) with no changes in bioavailable testosterone (as the primary outcome of the study).
Not only did recruiting adolescents for this study pose a challenge (in part due to widespread use of hormonal contraception) but also the impact on weight and biochemical hyperandrogenism were marginal at best.
Clearly, as the authors note,
“Innovative strategies are needed to recruit adolescents for studies aimed at assessing independent effects of diet on features of PCOS.”
Exactly what those innovative strategies may look like, remains an open question.
Although pelvic exercises and urological surgeries can go a long way in alleviating the symptoms, excess abdominal pressure directly resulting from excess abdominal fat, often exerts a physical force that no sphincter will withstand.
However, evidence that weight loss will actually improve urinary incontinence is hard to come by.
Thus, clinicians may wish to refer to the study by Subak and colleagues, published in JAMA Internal Medicine, which examines the effects of bariatric surgery on urinary incontinence.
The study involves around 2,000 patients form 10 US hospitals, who were followed after bariatric surgery for 3 years.
Before surgery, urinary incontinence (defined as at least weekly urinary incontinence episodes) was present in 49% of women and 22% of men.
At 1 year following surgery, these numbers were reduced to 18 and 10%, with a slight increase in year 3 to 24 and 12%, respectively.
Improvements were directly linked to the amount of weight loss as well as to whether or not the patient was mobile.
This study provides strong evidence in support of the notion that weight loss with bariatric surgery can markedly improve urinary incontinence in both men and women.
Whether or not non-surgical weight loss has similar effects remains to be seen.