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Fat science

Editorial note: In this blog-perspective, obesity expert Dr Robyn Toomath outlines the dogmas and arguments for the ‘individual-responsibility’ explanation and (lack of) solution to the obesity epidemic. She then points to the market failures that render (non-regulated) free-market solutions as doomed to fail. The views in this blog are expanded in greater depth in a book Dr Toomath is launching in Auckland and Wellington this month, Fat Science (Auckland University Press).


If you stop and ask people on the street, nine out of ten (including the overweight ones) will say that you get fat from over-eating and its no-one’s fault but your own. This is not just due to imperfect understanding of geno-environmental interactions, but because the notions of autonomy and self-control are deeply held (1). So when nihilistic biologists such as myself suggest there is no such thing as free will, it’s not just the libertarians but liberal intellectuals who are offended.

I need to remind myself of this tension between free will and socially determined arguments when I feel frustrated at the persistent framing of obesity as an issue of personal responsibility. But no matter how appealing the idea that we can change our body size if we choose to, the reality is that we can’t. At least, not most of us, and not permanently. Professor Sir Peter Gluckman, the Prime Minister’s Chief Science Advisor (and obesity expert), said in a recent speech that over his life time he has lost about 100kg in weight, and put about 95kg back on (2). If motivation and education were the keys to staying slim Sir Peter should be as thin as a rake (he’s not).

It’s all very well maintaining a fantasy if it makes us feel better but the personal responsibility myth causes great harm.

The most obvious harm is the stigmatisation and shame experienced by an overweight person. The impact of this can be quantified by looking at wages earned by fat and slim people, corrected for other factors. In a study of 25,800 people in the US, a woman weighing 30kg above ideal weight earned on average 9% less, equivalent to 3 years of work experience or a year and a half of education compared to a normal weight woman. The penalty for severely obese men was a 20% lower salary (3). Prejudice develops at a very young age and psychologist Andy Hill has documented marked aversion to obesity by children as young as nine and this appears to be getting worse with time despite increasing numbers of fat children (4). In the absence of effective treatments for obesity in children (despite Minister of Health Coleman’s assertions to the contrary), I share Children’s Commissioner Dr Russell Wills’ view that identifying obesity in the B4 school check will likely do more harm than good (5).

That is, a targeted individual-level approach to tackling obesity, which requires identifying overweight and obese people to start with, can perhaps do more harm (stigmatisation) than good.

A claimed feature of the current New Zealand Government is pragmatism. Surely the failure of a ‘personal responsibility’ approach to obesity would persuade a Government with its citizens’ best interests at heart (and future health budgets) to change tack? Most of the adult population is overweight (6), we have the fourth highest rate of childhood obesity in the world, we are the 3rd fattest of the OECD countries and there is no sign that obesity rates are flattening off (7). Britain is following Mexico and many States in the US with a tax on sugary drinks, but our Government is holding to a largely personal responsibility and free market ideology and remains resistant to what they see as ‘nanny state intervention’ (8,9).

The good news is that economic theory itself points to a way out. Governments need to intervene if one of four criteria of ‘market failure’ is met. The first criterion is skewing of the market by ‘externalities’. This refers, for example, to an individual making a decision which results in a cost which is borne by someone else. If you want to sky-dive or climb mountains, the risks associated with dying fall on you (though being injured and rescued is another matter). With obesity a person may choose to eat an unhealthy diet but if they develop obesity-related disease the costs of this are borne by society as well as that individual, and if the financial costs are too high, the government would have grounds to intervene. It is easy to make this case, e.g., in 2012 the annual cost to the New Zealand health system of obesity was estimated at NZ$624 million (10).

The second version of market failure occurs when ‘imperfect information’ perverts our ability to make a reasoned decision. Imperfect information certainly applies to confusing food labelling on processed foods. How do we decide if these products made from artificial ingredients are healthy? Governments seem interested in tackling food labels but the fact that the food industry has lobbied so hard to avoid these suggests that imperfect information works in their favour and may well be skewing the supply and demand equation (11).

The third category is ‘time-inconsistent preferences’, which often result in satisfying short-term goals over longer term ones (or what is sometimes referred to as a high discount rate). This could refer to planning to cook a healthy meal but succumbing to the temptation to eat from the junk food outlets that you pass on the way home. A way of partially correcting for this would be to ensure that healthy food was available in all places where unhealthy food is sold.

I’m most interested in the fourth category, ‘demerit goods’, meaning products like alcohol and tobacco and activities such as gambling which are dangerous or unhealthy. Governments should be bound to protect vulnerable individuals from the market forces of supply and demand for these things. With regard to obesity, foods which are energy dense and without nutritional value (apart from calories) are demerit goods. In terms of a vulnerable individual, it’s not just children but anyone with an inherited predisposition towards obesity that deserves protection.

With regard to obesity the unfettered free market in processed food has failed us and is costing our health system dearly. Individuals are largely unable to overcome their genetic predisposition (to eat more) and a highly obesogenic environment (that supports eating more and exercising less). If we want to fix this problem governments need, and are mandated, to apply smart regulation to the processed food market.

Public Health Expert Briefing (ISSN 2816-1203)


  1. Colin Bos, et al. ‘Understanding consumer acceptance of intervention strategies for healthy food choices: a qualitative study’. Biomed Central Public Health 3, 2013, p. 1073.
  2. -development-in-areas-of-post-normal-science-tickets-21441661587.
  3. John Cawley. ‘The impact of obesity on wages.’ Journal of Human Resources 39, 2004, pp.451-74.
  4. Andrew J. Hill and E.K. Silver. ‘Fat, friendless and unhealthy: 9-year old children’s perception of body shape stereotypes’. International Journal of Obesity and Related Metabolic Disorders 19, 1995, pp. 423-40.
  10. Anita Lal, et al. ‘Health care and lost productivity costs of overweight and obesity in New Zealand.’ Aust NZ J Public Health. 36, 2012; pp.550-6.
  11. Brussels Sunshine. ‘High time for CIAA to come clean on its lobbying.’ Brussels Sunshine, 23 June 2010, 

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