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.
Of all of the common complications of obesity, fatty liver disease is perhaps the most insidious. Often starting without clinical symptoms and little more than a mild increase in liver enzymes, it can progress to inflammation, fibrosis, cirrhosis and ultimate liver failure. It can also markedly increase the risk for hepatocellular cancer even in patients who do not progress to cirrhosis.
Now, a paper by Mary Rinella from Northwestern University, Chicago, published in JAMA provides a comprehensive overview of what we know and do not know about early detection and management of this condition.
The findings are based on a review of 16 randomized clinical trials, 44 cohort or case-control studies, 6 population-based studies, and 7 meta-analyses.
Overall between 75 million and 100 million individuals in the US are estimated to have nonalcoholic fatty liver disease with 66% of individuals older than 50 years with diabetes or obesity having nonalcoholic steatohepatitis with advanced fibrosis.
Although the diagnosis and staging of fatty liver disease requires a liver biopsy, biomarkers (e.g. cytokeratin 18) may eventually help in the detection of advanced fibrosis.
In addition, non-invasive imaging techniques including vibration-controlled transient elastography, ultrasound with acoustic radiation force impulse or even magnetic resonance elastography are fairly accurate in the detection of hepatic fibrosis and are the most reliable modalities for the diagnosis of advanced fibrosis (cirrhosis or precirrhosis).
Currently, weight loss is the only proven treatment for fatty liver disease. Pharmacotherapy including treatment with vitamin E, pioglitazone, and obeticholic acid may also provide some benefit (none of these treatments currently are approved for this indication by the UD FDA). Futhermore, the potential benefits of existing and emerging anti-obesity treatments on the incidence and progression of fatty liver remains to be established.
As Rinella points out,
“It is important that primary care physicians, endocrinologists, and other specialists be aware of the scope and long-term effects of the disease.”
Clearly, screening for fatty liver disease needs to be part of every routine work up of individuals presenting with excess weight.
This is why the recent paper by Nia Mitchell and colleagues from the University of Colorado, published in the American Journal of Preventive Medicine is of considerable interest.
The study looks at long-term weight loss of participants who joined Take Off Pounds Sensibly (TOPS), a US nonprofit, low-cost, peer-led weight-loss program between 2005-2011 (207,469 individuals) and consecutively renewed their annual membership at least once 74,629 (35.9%).
Mean weight loss for those who renewed their membership at least once was 6% and 8% for the 2,289 participants with 7 years of consecutive annual renewal.
Three points are probably worth emphasizing: for one, as with most weight loss programs, only a small proportion of individuals stick with it even for just a year (in this case about 35% which is still probably better than for most programs that I am aware of). Long-term members (in this case about 10%, who manage to stick with the program for at least 7 years) are even a greater minority.
Secondly, those who stick with the program in the long-term are able to sustain their benefit – of course it is hard to prove that this long-term benefit is actually causally related to the program – after all, the kind of people who make long-term commitments to a weight management program may well differ from the general public in other ways that may be important for their success.
Thirdly, the study illustrates that the average weight loss even for those who stick with the program over 7 years manage to keep off only about half of what is generally seen in long-term studies with bariatric surgery (about 20% weight loss over 15-20 years).
None of this takes away from the success of the TOPS approach to long-term weight management – it does however illustrate that even one of the best and longest running “lifestyle” management approaches to weight management, faces the usual challenges of attrition and plateauing weight loss at a level that may be less than what many living with severe obesity would consider a satisfactory outcome.
Kudos to TOPS for allowing this public analysis of their data – few other weight loss programs would dare to do the same.
Note: see comment #1
One of the most persistent notions about equating caloric deficit to weight loss is the 3500 Cal “rule”.
I have previously posted about why this is nonsense and not exactly helpful when it comes to thinking about clinical weight loss or weight (you’re dealing with physiology NOT physics!).
Now, Nicholas Gwerder, a student from the University of Sacramento, in his Master Thesis, has apparently reviewed the literature on this and concludes that if anything, one pound of weight loss comes closer to 4,500 calories.
Gwerder reaches this conclusion by analysing data from 28 studies in which he compares the theoretical weight loss to the actual weight (and fat) lost in these studies.
Although, I do not have access to Gwerder’s Master Thesis, here is what he says in the summary:
“The energy equivalent of body weight loss varied considerably, dependent upon the constituent portions of fat, water, protein, carbohydrate and mineral lost. Adipose tissue also varied with type and was dependent upon the composition of lipid, water, and protein. The most valid theoretical equivalent for a pound of fat was calculated at 4,423.90 kilocalories based on in vivo extraction of human intracellular lipid samples.”
Thus, as Gwerder points out, the 3,500 per pound notion tossed around (including by a number of guidelines and associations)
“…severely underestimates the caloric values needed to achieve desired fat mass loss. This use of the proper caloric value for fat mass loss has the potential to improve exercise and nutrient recommendations for achieving healthy body fat values.”
Thus, if this number holds true, a daily 500 Cal deficit maintained over 10 weeks will not give you a 10 pound weight loss, but rather only about 7.5 lbs.
All the same, in practice over time this never really works out, not just because of the individual variability (Gwerder notes about 20% variation in this relationship) but because as you reduce your caloric intake, your individual metabolic requirements will very quickly shift to living off fewer calories, which means that pretty soon into your diet, the initial 500 Cal deficit is no longer a deficit (thank your physiology). This is the feared weight-loss plateau – the frustration of every dieter.
So, whether 3,500 or 4,500 Cal per pound, the relationship between calorie restriction and weight loss is not linear and thus extrapolating the amount of expected weight loss based on this deficit seldom works out in practice.
Indeed, I know from my patients that this “rule” is a matter of endless frustration and seldom helpful.
Managing weight is not simply about energy in and energy out.