Regular readers will be well aware of the limitations of applying BMI to obesity diagnosis – after all, BMI is a measure of size, not health. If there is one thing we have learnt, it is that good health is possible over a wide range of shapes and sizes and that using a static measure like BMI, will mean overdiagnosing obesity in people who have no relevant impairment in health and underdiagnosing obesity in people who would in fact stand to gain from obesity treatments.
As I have noted before, in a medical context, obesity should be defined as, “the presence of excess or abnormal fat tissue that impairs health“. In clinical practice this would mean asking the question (irrespective of BMI), “does this patient have a health impairment that is likely to get better with obesity treatment?” If yes, the patient most likely has obesity and should be offered obesity treatment. If not, the patient does not have obesity and will be unlikely to benefit from obesity treatment.
This approach would identify both the “high-BMI” individuals with medical issues likely to get better with obesity treatment, as well as the “normal-BMI” individual, who may stand to benefit from obesity management.
Not only will this “common-sense” approach to diagnosing obesity identify individuals over the entire BMI range, who would potentially benefit from obesity treatments, but will also help set specific targets for assessing the success of treatment.
Thus, if the presenting problem is hypertension (say in a patient with a BMI of 24 with clear signs of increased belly fat – but skinny arms and legs), then the goal of obesity treatment would be to lower blood pressure, rather than to simply reduce body weight. Similarly, a patient with a BMI of 24 with type 2 diabetes would likely benefit from obesity management in terms of better diabetes control. If, in these patients, effective obesity treatment (as measured by weight loss) does not lead to better hypertension or diabetes control, then their health issues are probably not related to their body fat, meaning that they probably don’t have obesity.
Thus, the obesity diagnosis and management algorithm would look something as follows:
Does the patient have any impairments in health likely to improve with obesity treatment? (list impairment/s)
if no, patient does not have obesity and does not need any obesity intervention (irrespective of BMI).
If yes, offer obesity treatment to see if this improves the health issues.
If health condition improves, continue obesity management.
If health condition does not improve, reconsider the obesity diagnosis (problem may be entirely unrelated to body fat). discontinue obesity treatment.
Basically, BMI, or for that matter body weight, does not have to enter the equation. The only thing that matters, is whether or not the presenting health problem actually responds to obesity treatment or not.
Fortunately, we have a long list of health issues that we know will improve with obesity treatment (e.g. hypertension, type 2 diabetes, sleep apnea, psoriasis, musculoskeletal pain, knee osteoarthritis, PCOS, etc. etc.), thus making clinical assessment of whether or not someone may have obesity relatively straightforward. Considering obesity treatments to better manage these conditions makes a lot of sense. On the other hand, treating obesity simply to lower body weight (without any measurable health benefits) does not.
As any clinician knows, changes in appetite are an important part of taking a good medical history. While loss of appetite is generally a warning sign that your patient may be seriously ill (sometimes, loss of appetite is the first sign of an illness – physical or mental), an increase in appetite may likewise indicate a serious problem.
In order to assess whether the reported change in appetite is clinically relevant, it is important to follow any appetite question with a “weight change” question. Thus, if a patient reports loss of appetite, an obvious follow-up question would be to ask whether the patient has lost weight. In contrast, if the patient reports an increase in appetite, it is only fair to ask if this has been associated with weight gain. In fact, even if the patient says that their appetite has not changed, it would be fair to ask if their weight has been stable.
While some patients (and clinicians) may be wary of bringing up the issue of weight, no patient in my experience has ever objected to being asked about their appetite. In addition, no patient has ever objected to being asked a weight question after first being asked about their appetite.
Thus, in my experience, the easiest way to start a conversation about body weight, is to begin by asking about appetite.
A typical conversation could run as follows:
Clinician, “So have you notice any change in appetite?“
Patient, “Funny you should ask, yes, I seem to be particularly hungry after dinner, I often have to eat a sandwich before I go to bed“
Clinician: “So have you noticed any change in your weight?“
Patient: “Well, I think I may have gained a few pounds since I last saw you“
Clinician: “Is that something that concerns you, something you’d like to talk about?“
Obviously, the tone of this conversation needs to be completely non-judgemental and if the patient is not interested or willing to talk about this issue, we can always park this discussion for later.
In any case, if you’ve ever wondered how to start a discussion about body weight with a patient, try first talking about appetite. As a mnemonic, I call this the A&W (Appetite & Weight) approach to discussing body weight.
Can Exercise-Induced Modulation of the Tumor Physiologic Microenvironment Improve Antitumor Immunity?
Both obesity and sedentariness have been linked to increased risk for a wide range of cancers. While there is some evidence that weight loss (e.g. through bariatric surgery) can reduce the incidence of and deaths from malignancies, the role of exercise on cancer morbidity and mortality is less clear. Although a growing body of literature suggests that increased physical activity can reduce the mental and physical stress of living with cancer, its role in directly influencing the malignant process is less clear.
Now, a paper by Xiaojie Zhang and colleagues, published in Cancer Research, discusses the many ways in which exercise may potentially promote the body’s ability to fight cancer by modulating the tumor microenviroment.
As the authors point out, “Preclinical and human studies suggest that exercise elicits mobilization of leukocytes into circulation (also known as “exercise-induced leukocytosis”), especially cytotoxic T cells and natural killer cells. However, the tumor physiologic microenvironment presents a significant barrier for these cells to enter the tumor and, once there, properly function.“
Among the mechanisms by which exercise can alter immunological response to tumors, the authors include positive changes to the tumor microvasculature as well as the tumor microenviroment including decreased hypoxia, hypoglucosis, lactosis, and reduced pH. For each of these potential mechanisms (that are likely to work in concert), the authors discuss current evidence from animal models that would support these potentially beneficial effects of exercise.
While we have yet to see a definitive controlled study on the long-tem benefits of exercise treatments on cancer survival (and not just rehabilitation and well-being), the authors make a strong case that such studies are perhaps long overdue. In addition, “Rigorous studies that elucidate the link between exercise and immune cell function in the tumor microenvironment and in the periphery will also serve as a guide of how to implement exercise in the context of immunotherapies that harness the immune system against cancer. ”
Every now and then, a landmark study comes along that definitively answers an important question, and, perhaps more importantly, lays to rest many of the theories that float around both in the scientific literature and the lay media.
It would perhaps not be superlative to note that just such a study by Kevin Hall and colleagues (presented just a few weeks ago at the 6th Biennial Canadian Obesity Summit) has now been published in Cell Metabolism.
The study examines what happens to calorie intake and body weight when people have free access to a diet largely composed of ultra-processed foods vs. a diet composed of unprocessed foods. Ultra-processed foods have been described as “formulations mostly of cheap industrial sources of dietary energy and nutrients plus additives, using a series of processes” and containing minimal whole foods.
Importantly, the two diets were carefully matched for presented calories, energy density, macronutrients, sugar, sodium, and fiber. Although protein, carbohydrate, and fat content were virtually identical, the ultra-processed foods differed substantially from the un-processed foods in the proportion of added to total sugar (∼54% versus 1%, respectively), insoluble to total fiber (∼77% versus 16%, respectively), saturated to total fat (∼34% versus 19%), and the ratio of omega-6 to omega-3 fatty acids (∼11:1 versus 5:1).
The 20 weight stable healthy participants, who spent over four weeks in an in-patient metabolic ward, were instructed to consume as much or as little of the foods offered with one diet over a two week period before switching to two weeks of the other diet (in a random cross-over fashion).
In short, during the 2nd week of eating the ultra-processed diet, subjects consumed about 500 kcal more per day than during the 2nd week of the unprocessed diet. This was accompanied by an almost 2 lb weight gain on the ultra-processed diet (whereas weight reduced by about the same measure on the unprocessed diet). This response was seen irrespective of which diet came first or of the baseline BMI of participants.
To set this study in perspective, there have long been theories about how the increased availability of ultra-processed foods may be playing a causal role in the obesity epidemic. Thus, as the authors point out, “Ultra-processed foods may facilitate overeating and the development of obesity because they are typically high in calories, salt, sugar, and fat and have been suggested to be engineered to have supernormal appetitive properties that may result in pathological eating behavior. Furthermore, ultra-processed foods are theorized to disrupt gut-brain signaling and may influence food reinforcement and overall intake via mechanisms distinct from the palatability or energy density of the food.” As plausible as these “theories” many seem, to date, this hypothesis has never been tested in a well-controlled randomised trial.
The increased caloric consumption on the ultra-processed diet was not explained by greater palatability or familiarity of the ultra-processed diet, or differences in reported hunger, fullness, satisfaction, and capacity to eat. However, the rate of eating (measured as calories or grams per minute) was higher on the ultra-processed diet (as I have noted previously, the problem with fast food is more the “fast” than the “food”).
As the authors note, “The perpetual diet wars between factions promoting low-carbohydrate, keto, paleo, high-protein, low-fat, plant-based, vegan, and a seemingly endless list of other diets have led to substantial public confusion and mistrust in nutrition science. While debate rages about the relative merits and demerits of various so-called healthy diets, less attention is paid to the fact that otherwise diverse diet recommendations often share a common piece of advice: avoid ultra-processed foods.” Clearly this study strongly supports the idea that cutting ultra-processed foods from your diet will likely help avoid excess caloric intake and subsequent weight gain.
There is however one caveat: based on the cost of ingredients obtained from a local supermarket, the weekly cost for ingredients to prepare 2,000 kcal/day of ultra-processed meals was estimated to be $106 versus $151 for the unprocessed meals. This would mean a food bill that is 50% higher for the average household. In addition, there is a time cost for meal preparation (and chewing) of the unprocessed food diet.
Be that as it may, any diet that reduces the amount of ultra-processed foods in your diet is likely to help you better manage your caloric intake and reduce inadvertent weight gain. Whether or not such a diet can be implemented at a population level remains to be seen but clearly the more dependent we remain on ultra-processed foods, the harder it will be to contain the obesity epidemic.
As readers are well aware, the current public and health policy discussions around obesity are centred around the notion that obesity is largely a “lifestyle” problem that can be addressed largely by population-wide and individual-based initiatives focussed on promoting healthy eating and increased physical activity (eat less – move more).
Irrespective of whether or not this is intended, the impact of this simplistic narrative on the lives of people living with obesity are clear: not only does this narrative squarely place the blame (eating too much, not moving enough) on individuals living with obesity, it also largely ignores the vast body of research that points to the complex interplay of biological and psychosocial drivers of obesity, most of which are beyond the control of the individual. This narrative is also now recognised as the root cause of weight bias, stigma, as well as health and social inequalities that can reach the level of outright discrimination.
Importantly, this simplistic narrative, together with the failure to recognise obesity as a chronic disease (like type 2 diabetes or hypertension), by governments, health systems, public and private payers, the public, and media has a trickle-down effect on access to treatment for those living with this disease. As outlined it the Obesity Canada’s Report Card on Access to Obesity Treatment for Adults in Canada 2019, the vast majority of Canadians lack access to behavioural interventions, medically supervised weight management using meal replacements, anti-obesity medications, and bariatric surgery.
In an attempt to change this narrative, Obesity Canada has now assembled a large (and growing) coalition of stakeholders, who are willing to speak with a united voice on obesity and advocacy efforts.
Members of the coalition support the notion that obesity is, “a chronic disease that is defined by having adipose tissue (body fat) that impairs health. It is not solely based on weight, BMI or body size but rather the degree of physiological, functional, and psychosocial barriers that affect one’s holistic health”
Overall, the mission of this Advocacy Network is to unite and align key organizations and the community around education, policy, and legislative advocacy efforts in order to elevate the obesity as a chronic disease narrative on the national agenda. It is through this change in narrative, that people affected by obesity may gain access to the same medically necessary and covered management avenues afforded to all others who suffer from chronic diseases.
All of this serves the ultimate goal to reduce weight bias and obesity stigma, improve access to evidence-based care, improve standards of quality care and rehabilitation, and educate health care professionals, policy makers and the public about obesity as a complex chronic disease.
For more about the Canadian Obesity Advocacy Network and on information how your organisation can join this coalition contact Obestiy Canada at firstname.lastname@example.org
p.s. to date, representatives of the following organisations have participated in meetings of the Canadian Obesity Advocacy Network:
- Canadian Medical Association
- Canadian Society for Endocrinology and Metabolism
- Canadian Association of Bariatric Physicians and Surgeons
- Heart and Stroke Foundation of Canada
- Canadian Psychiatric Association
- Canadian Psychological Association
- Canadian Association of Occupational Therapists
- Obesity Canada
- Diabetes Canada
- Hypertension Canada
- Dietitians of Canada
- Canadian Network for Health Behavior Change
- Exercise is Medicine Canada
- Novo Nordisk Canada
- International Behavioural Trials Network
- Yukon Medical Association
- Saskatchewan Medical Association
- Centre for Health Economics and Policy Analysis
- Canadian Human Rights Commission
- National Aboriginal Diabetes Association
- Canadian Guidelines for Cardiac Rehabilitation and Cardiovascular Disease
This week I am in Dublin for the 7th Conference of the Association for the Study of Obesity on the Island of Ireland (asoi), which co-incides with the 2018 European Obesity Day (Saturday, May 18).
As any “day”, the aim of the Obesity Day is to draw attention to and foster discussions about obesity, its causes, and possible solutions.
The accompanying website provides links to a number of interesting and helpful resources, including Obesity Facts, messages to Policy Makers, Patient Perspectives, Addressing Obesity Stigma, and Patient and Expert videos.
How much these activities change the narrative and actions on obesity remain to be seen, but no doubt, any initiative that promotes greater awareness and discussion of the science of obesity is much appreciated.
To anyone working in obesity, it is no secret that obesity is now far more common in rural (and suburban) areas (at least in industrialised countries) than in big cities. This may appear counterintuitive, as access to food services is much greater and easier in cities than in rural areas. In contrast, there is a wide-spread assumption that people living in rural areas mainly consume produce from their own farms and gardens, and have less access to ultra-processed and packaged food.
Now, a paper by the international NCD Risk Factor Collaboration, published in Nature, shows that rural obesity, even in many low- and middle-income countries (LMICs), is rising much faster than in urban populations.
The study collates 2,009 population-based studies, with measurements of height and weight in more than 112 million adults, to report national, regional and global trends in mean BMI segregated by place of residence (a rural or urban area) from 1985 to 2017.
The data shows that, with the exception of women in sub-Saharan Africa, more than 55% of the global rise in mean BMI from 1985 to 2017—and more than 80% in some low- and middle-income regions—was due to increases in BMI in rural areas.
Thus, “these trends have in turn resulted in a closing—and in some countries reversal—of the gap in BMI between urban and rural areas in low- and middle-income countries, especially for women. In high-income and industrialized countries, we noted a persistently higher rural BMI, especially for women.”
The authors attribute this trend to the urbanisation of rural life, which includes not only the decreased need for physical labour thanks to agricultural mechanisation, dependence on cars, rising income, and the increased availability and consumption of highly processed calorie-dense foods.
In contrast, “The lower urban BMI in high-income and industrialized countries reflects a growing rural economic and social disadvantage, including lower education and income, lower availability and higher price of healthy and fresh foods, less access to, and use of, public transport and walking than in cities, and limited availability of facilities for sports and recreational activity, which account for a significant share of overall physical activity in high-income and industrialized countries.“
Clearly, this alarming trend poses new challenges for public health initiatives to curb the obesity epidemic, which have thus far largely (albeit with little effect), focussed on urban populations.
Although not discussed in the paper, this trend also poses new challenges for the health care system, which is even less poised to deliver evidence-based obesity treatments, which may often require the support of specialists (e.g. dietitians, obesity specialists, mental health professionals, or even surgeons), than in urban centres.
Last week, I had the pleasure of sitting on the thesis defence committees of two extraordinarily dedicated young trainees, currently completing their medical residencies in obstetrics and gynaecology. Both theses focussed on issues related to obesity within the obstetric community as well as the implications of obesity for the care of women during the gestational period and during delivery (more on these theses in coming posts).
For those interested in this topic, I would like to draw your attention to a short review paper by Cecilia Jevitt, Chair of the Midwifery Program at the University of British Columbia, published in the Journal of Perinatal and Neonatal Nursing.
Although the paper focusses on the social determinants of health that underly a substantial proportion of the risk for developing obesity (these include socio-economic disparities
in employment, education, healthcare access, food quality,
and availability), the paper also looks at many of the environment and biological factors that may promote obesity including environmental toxins, epigentics, and the microbiota.
As for the impacts of excess body fat on pregnancy, Levitt lists over 30 conditions that can affect the pregnancy, delivery, and the post-partum period, threathening the health of mother and child, which are far more common in women with obesity.
This is not to say that many of these problems can not also be encountered in the care of women without obesity, however, excess body weight makes these conditions far more likely and often much more difficult to manage.
As Levitt points out, reducing the risk for obesity in the first place would need comprehensive changes at the policy level that not only address issues related to food and activity but also the socio-economic and other social determinants of health that disproportionately affect women of lower socio-economic status.
As currently, no such policies are in sight, those charged with the care of women of childbearing age will continue having to watch for and deal with the increased risk for adverse outcomes in women with excess weight – a challenge that is only slowly (as evidenced by the theses mentioned above) coming to the centre of attention of obstetric health professionals.
On the positive side, Levitt reminds us that, “Although obesity places women at risk for numerous morbidities, most women with obese BMIs [sic] complete pregnancy and birth without complications.” Improved training of health professionals in the care of women with obesity can no doubt further decrease the risk to both mother and child.