Some things are not supposed to be controlled. They are not our personal responsibility. Weight is one of them. I repeat, your weight is not your personal responsibility or choice.

This may sound controversial because we have been taught that our weight is inversely correlated with health. But this is oversimplified and largely untrue.

We cannot “healthily” manipulate what’s not supposed to be manipulated.

Your weight, much like your height or eye color is predetermined, by genetics. But it’s influenced by environment, your health, your diet history, & both diet and exercise. The latter two are only small contributors. With all the other factors that you have no influence over, it’s futile trying to micromanage. If you go too far in one direction, your body will fight it to live in homeostasis.
If you are genetically built to live in a larger body you will never have a “healthy” smaller body regardless of all the exercise or dieting you do. It just won’t work, the body will fight it and you will see all of the negative effects of this.
The larger body you were born into was healthy.

What’s prompted this post is following announcements from the UK governement they may financially reward weight loss in a campaign to “fight obesity”. They talk about providing incentives with subscriptions to restrictive diets such as weight watchers and slimmers world. This is such a harmful campaign. Further more, this announcement was released in the middle of national eating disorder awareness week, the theme of this was Binge Eating Disorder (BED) (1). Binge eating disorder sufferers are already statistically less likely to seek help than any other eating disorder, despite it being the most prevalent eating disorder. 1 in 50 people in the UK are expected to be affected by BED. A staggering 40% of people in the US following weight loss programmes meet the criteria for BED (2). BED is a serious mental disorder with physical side effects. People with BED, consume large quantities of food quickly without feeling in control, it is NOT the same as “over indulging”. Patients often restrict heavily between binges which fuels the cycle. Often patients with BED do live in larger bodies, they are “obese” by societies definition. The UK government’s message is damaging and harmful to those with BED. Weight stigma is a huge problem in society and in healthcare. Patients with BED are stigmatised, invalidated and often do not seek help. They are too commonly prescribed restrictive diets as an answer. However evidence has proven time after time, binges follow restriction.

Campaigns like this, will have a ripple effect, making access to treatment all the more difficult. More patients are likely to develop eating disorders such as BED, following restrictive diets will not end well.

I anticipate- the “obesity crisis” will increase after everyone regains the weight they lose and more, furthermore it is encouraging disordered eating, which will raise the incidences of eating disorders. Without tackling the core issue of weight stigma, many of those eating disorders will go undetected. “Atypical anorexia” is another diagnosis used by the DSM-V ( diagnostic, statistic manual psychiatric disorders) to diagnose patients with anorexia but are not underweight according to BMI. However Anorexia can manifest in any body shape or size. The difference is the weight stigma those suffering with anorexia in a larger body experience. They are often congratulated for their disordered behaviours, not taken seriously making access to help more difficult.

Let’s discuss BMI. The BMI was invented by a Belgian mathematician in the early 19th century. Lambert Adolfe Quetelet was a mathematician, statistician, sociologist with an interest in anthropometric sciences (3). Anthropometric study is essentially is body measurement study. He had no medical training. He has since been heavily criticised for his population studies of BIPOC and labelling people of colour as “separate species”. One of Quetelet’s areas of interest was in the “average man”, he used data including height and weights to help him determine this.
His studies were largely population based, cohort studies, mostly including white European males. He developed a formula to calculate a ratio of body weight to height squared, after an observation that there were weight and height variations within populations. More specifically that weight did not appear to be directly proportional to height, he discovered weight varied in proportion to height squared. This became known as the Quetelet index, before Ancel Keys renamed it the BMI in 1972. Ancel keys a famous physiologist, attempted to prove correlation with obesity, BMI and poor health. He did not succeed.
The BMI was not used to determine health it was to show “population averages”. It was designed to track population’s weights. It did not measure adipose tissue, or account for muscle. Once again it primarily referenced white European men.

It can therefore not be used as a predictor of individual health status, at best it’s a population screening tool, particularly if that population is white, male and European.
It identifies potential “population risk” of certain diseases such as diabetes, coronary artery disease. However an individual’s BMI, in isolation is not helpful, as a person can have a high BMI but very little visceral fat which has been associated as a greater risk factor. Muscle mass contributes significantly to weight and therefore BMI.

Interestingly, the optimal BMI for mortality is actually within the “overweight” category on the BMI scale. The most optimal BMI statistically from latest studies is actually 27 (4). Yet the BMI scale has not been updated to reflect the definition or risk stratification. Go figure.

The more I learn the less I know, but the more I want to know. Nutritional science is an incredibly complex field of science. It’s also a very difficult area to interpret. I am relatively confident in my ability of interpreting scientific papers coming from an oncology background, but I do not feel equipped to interpret and advise patients on nutritional science. The studies I tend to go to as my default for information and decision making in my career comes form the “gold standard” of evidence, which is data from meta-analysis of randomised control trials.

Meta-analysis analyses data from big randomised trials. (For anyone non medical or non scientific, randomised control trials (RCT) are the holy grail of investigating an intervention. It involves studying two groups, randomised to receive the intervention or a placebo. The difference in the two groups is studied. For example a group of patients with diabetes are randomised to receive a new blood sugar lowering drug. One group gets the drug, the other does not. The changes in their blood sugars are observed. You can control for variables because people are selected based upon specific characteristics, such as age, starting blood sugar levels for example.

Nutritional science is difficult to interpret, because, the studies are largely cohort studies (population based), i.e. you cannot ethically conduct randomised control trials in this field (i.e. you couldn’t restrict a particular nutrient from a group). You cannot control the variables that vary like you can in an RCT (you have no idea how much carbohydrate someone eats compared to the next or how their body actually uses it). Interpreting them is difficult. Therefore I feel uncomfortable ever promoting something I have little or no understanding in. Examples that have come from nutritional science are: the “carbs are bad”, high fibre diet and colorectal cancer risk reduction, ketogenic diet, vitamin E and reduced risk of developing alzheimers. But, unlike medical studies, we cannot control variables in the studies and then apply them to individuals or draw cause and effect. Vitamin E, has been shown to reduce the risk of Alzheimers, but when you look at how, it is not actually understood. Therefore taking a supplement that is not that same as the vitamin E absorbed from a persons diet is just not generalisable.

At medical school we get minimal training on nutrition, yet we are asked important questions that I feel we are ill equipped to provide. I find it concerning when people advocate things such as low carb diets as a one size fits all, pun intended. It’s an issue, there are so many shades of grey. However I am confident in my knowledge and the evidence surrounding BMI, and weight bias. Weight bias is dangerous and our lack of understanding or inappropriate use of nutritional science is concerning. Nutrition is also a luxury and we do not acknowledge this. I am a white middle class female, I acknowledge my privilege, what this means is I am fortunate to be able to choose what I eat. Many people are not as fortunate and they eat what they can, therefore prescriptive diets by nature are also not available to a large population, and yet they are stigmatised for choices that are actually not really a choice.

The BMI was never intended to be used as the measure of individual health, that is is used for today. It is also not applicable to a wider population as it included a narrow cohort. Yet we base such importance on a number that never had any intention for medical use.

For anyone who has received weight stigma or bias, please understand you are not alone. Binge eating disorder is serious and everyone should be able to access help. We can be healthy at any size.

References:

1. BEAT Eating disorder Awareness Week: https://www.beateatingdisorders.org.uk/edaw
2. BEAT information page BED: https://www.beateatingdisorders.org.uk/types/binge-eating-disorder
3. Quetelet index: https://pubmed.ncbi.nlm.nih.gov/17890752/
4. BMI associations and mortality: Change in Body Mass Index Associated With Lowest Mortality in Denmark, 1976-2013 Afzal, S., Tybjærg-Hansen, A., Jensen, G. and Nordestgaard, B., 2021. Change in Body Mass Index Associated With Lowest Mortality in Denmark, 1976-2013. https://jamanetwork.com/journals/jama/fullarticle/2520627?resultClick=1