A couple of months ago, I wrote a post called Is the ‘Health At Every Size’ movement helping or hurting?, in which I dissected the arguments of Health At Every Size (HAES) proponents. I won’t rehash those arguments and my responses to them – just read the original post, if you’re interested.
However, during a consultation last week with one of my clients, who has been struggling to stick to the healthy eating and lifestyle habits which she knows she needs to adopt in order to lose weight, the topic of plus-sized models came up.
Plus-sized models including Tess Holliday, who wears a US dress size 22 or 3x (roughly equivalent to a size 26 in Australia) have amassed huge social media followings as well as generating massive interest in traditional print and online media.
As well as advocating for body acceptance, many of these models have been outspoken in insisting that their health is not adversely affected by their body fatness. And this was the question that my client raised with me: is carrying excess body fat truly dangerous to her health, and is it really worth the considerable effort to reduce it?
Advocates of HAES argue that studies linking higher weight status with adverse health outcomes are flawed, and cite research such as a 2013 meta-analysis involving nearly 3 million individuals that found that being overweight (body mass index [BMI] 25-<29) was associated with lower all-cause mortality (i.e. lower risk of dying from any cause) being normal-weight (BMI 18.5-<25) and that being in the obese I category (BMI 30-35) was not associated with higher mortality.
It’s certainly true that there are many sources of potential error in studies that have sought to examine the relationship between body size and health outcomes.
The authors of a study published in JAMA Network Open in November 2018 titled ‘Association of Obesity With Mortality Over 24 Years of Weight History: Findings From the Framingham Heart Study’ were well aware of these methodological flaws and potential sources of confounding, which they sought to avoid when they designed their own study. These include:
- Confounding by illness, or reverse causality: many illnesses which shorten life expectancy also cause people to lose weight (e.g. many types of cancer), so a study which examines weight status at a timepoint when a health condition has already developed may falsely conclude that higher weight reduces the risk of dying.
- Severe exclusions of data: some criteria that are used to mitigate the risk of reverse causation bias, such as delaying the beginning of analysis until several years after study entry and eliminating individuals with a preexisting disease at entry, may reduce the precision and generalisability of the findings. In addition, some diseases are caused by obesity itself; excluding people with pre-existing diseases would result in the association between overfatness and poor health outcomes being diluted.
- Recall bias: people tend to be less than honest when asked to report on anything to do with their health, and this extends to underreporting their weight. Studies that rely on self-reported BMI are therefore likely to generate misleading outcomes.
Awareness of these potential sources of confounding and error informed the study design: a prospective cohort study (i.e. long-term follow-up study of a defined group of people) in which weight and height was measured by the researchers rather than self-reported by participants.
The study population was the original and offspring cohorts of the Framingham Heart Study, a long-running research project that recruited over 5000 men and women from the town of Framingham, Massachusetts in 1948, and has been following them, and subsequently their children and grandchildren, ever since.
The Framingham Study population helped researchers identify the major CVD risk factors – high blood pressure, high blood cholesterol, smoking, obesity, diabetes, and physical inactivity – as well as bringing to light valuable information on the effects of blood triglyceride and HDL cholesterol levels, age, gender, and psychosocial issues.
To conduct this study, the researchers included 6197 participants from the original and offspring cohorts of the Framingham Heart Study for whom BMI data were available at multiple time points (measured by health professionals every 2 years for the original cohort and every 4 to 8 years for the offspring cohort) along with health-related information gathered at each examination.
The researchers were particularly interested in the relationship between the maximum BMI that participants had reached at any point in their lives, and their mortality risk, partly because of the impact that being overweight or obese has on the risk of many potentially life-threatening diseases, and partly because of their concern to eliminate confounding by reverse causality.
The findings were very clear:
“A monotonic association was observed between maximum body mass index measured over 24 years of weight history and subsequent mortality, with increasing risks observed across the obese I and obese II categories compared with the normal-weight group… Maximum BMI in the normal-weight range was associated with the lowest risk of mortality in this cohort, highlighting the importance of obesity prevention.”
Or, in plain English, the fatter participants were at any point in their lives, the more likely they were to die before their time; and those who had never been overweight at any point in their lives were the most likely to still be alive by the end of the study.
Specifically, participants in obesity class I (BMI 30 to <35) had a hazard ratio of 1.27 meaning they were 27% more likely to be dead by the end of the study follow-up period than participants in the normal-weight category; obese II participants (BMI 35 to <40) had a hazard ratio of 1.93 meaning they were almost twice as likely to be dead.
The researchers also calculated mortality rates for participants who were of normal weight by the end of the study period but had previously been overweight or obese. Individuals who never exceeded normal weight throughout the entire study period had a mortality rate of 27.93 per 1000 person-years, but those who had previously been overweight or obese had mortality rates of 47.48 and 66.67 per 1000 person-years, respectively.
At 165 cm and 138 kg, plus-sized model Tess Holliday has a BMI of almost 51, placing her in obesity class 3 – heavier than any of the participants in the Framingham study. Sadly for her, the statistical probability of her enjoying a long and healthy life is low, even if she loses a substantial amount of weight in future.
When I read that she “embraces the word ‘fat’ and advocates that people should be able to eat as much and whatever they want without suffering from social ostracism“, I feel very conflicted.
Certainly no one should suffer social ostracism for overeating junk food; after all, multinational food corporations spend vast amounts of money developing and marketing ultraprocessed foods that are expressly designed to be highly addictive, and there is strong evidence that some people are more genetically predisposed both to become addicted, and to gain more weight as a consequence of overconsumption of these foods, than others.
But promoting such behaviours to others, under the guise of ‘fat acceptance’, threatens the health and even the lives of potentially hundreds of thousands of individuals, particularly vulnerable and impressionable young females who are caught in the ‘pleasure trap’ of overeating ultraprocessed food and consequently are struggling with their weight.
The client who prompted me to write this article is bright, capable, and the mother of two young children. I want her to enjoy the longest, healthiest life possible so that she can achieve her full potential and see her children grow up and have children of their own.
The weight (pardon the pun) of the scientific evidence that we have so far indicates that she’ll have the best chances of doing that if she eats and lives in such a way that she achieves and maintains a body weight in the normal BMI range.
Fortunately, the evidence also shows that eating a wholefood plant-based diet helps you lose excess body fat and maintain a healthy weight without restricting calories or eating tiny portions. Not coincidentally, it’s also the dietary pattern associated with the lowest risk of developing chronic diseases that shorten your life expectancy.
No one needs to deprive themselves in order to lose weight; a wholefood plant-based diet gives you the best of all possible worlds: an abundance of delicious food that allows you to lose weight healthfully while maximising your potential lifespan.
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