26 Jul 2018 Overfed but undernourished: the obesity paradox
Obesity is posing a significant threat to public health not only in the UK, but also in many countries across the globe.
One in five 4-5 year olds and one in three 10-11 year olds are overweight or obese in England. Just this week Public Health England (PHE) announced record numbers of children are leaving primary school severely obese [1, 2]. In addition, over two thirds of the adult population are now overweight or obese [3].
Evidence shows unhealthy weights can have significant negative impact on our short and long-term health. In addition, obesity is a notable risk factor for many diet-related illnesses including type 2 diabetes, cardiovascular disease, hypertension and stroke [4].
What is less known, rather, is the growing body of evidence that suggests obesity is also a risk factor for a number of nutritional deficiencies. Surprising as this may be – given that the majority of obese individuals consume over the recommended daily intake of calories. Furthermore, when most people think of nutrition deficiencies and undernutrition they think of impoverished countries, underweight individuals and a state of simply not having access to or eating enough food.
A recent study has found that overweight and obesity can correlate with being deficient in a wide range of essential vitamins and minerals – such as iron, calcium, magnesium, zinc, copper, folate and vitamins A and B12. Low intakes of these nutrients can lead to development of chronic diseases and conditions, such as type 2 diabetes, iron-deficiency anaemia, stunted growth and even scurvy (lack of vitamin C) and rickets (lack of vitamin D and calcium) [5].
The term ‘modern malnutrition’ was coined to represent this new trend of malnutrition, whereby obese individuals are suffering from the same nutritional inadequacies as the hungry and underweight.
But how can you be overfed, overweight or obese, but at the same time undernourished?
A higher BMI has been linked to a number of metabolic changes that may negatively impact our adsorption and metabolism of vitamins and minerals. For example, a large study a few years back found that higher BMI that caused lower vitamin D levels [6]. Furthermore, metabolic changes that occur in obese individuals may actually increase the requirements for certain nutrients [7, 8].
However, there is more concern about the quality of the diets that is fuelling this confusing trend. As the saying goes, it is quality, not quantity and this certainly applies to our diet too.
Overfed but undernourished – how is this possible?
One of the reasons why it may be a difficult concept to understand is that our knowledge and understanding of calories is limited. Nutritional science has long depicted that all calories are created equal and with the right amount of caloric intake, we should receive all the nutrients we require and therefore it would be difficult to be malnourished.
However, there is growing evidence to suggest a calorie is not just a calorie and the sooner we move away from the narrow view of energy intake and expenditure, the better we understand the complexities of diet and obesity. The quality of calories in also important, and we should be encouraging the public to consider the other nutritive value of foods (saturated fat, protein, fibre or vitamin C) when choosing food and drink – not just the calorie intake.
Unfortunately, the typical Western diet is low in fresh fruits, vegetables and whole grains, yet includes high levels of refined, processed and sugary foods. The latter are typically high in calories (or, empty calories as many call them) and not much else, thus often referred to as ‘energy dense (high in calories) and nutrient poor (low in nutritive value) diet. Energy-dense foods are typically high in fat (e.g. butter, oils, fried foods), sugars or starch, while energy-dilute foods have a high water content (e.g. fruits and vegetables). We know that a high intake of energy-dense foods promotes weight gain, and that the likelihood is these foods are being regularly consumed by the overweight and obese population.
These diets are also typically white, processed goods such a white bread or pasta – which have had the fibre removed during processing, along with iron and many important B vitamins to produce a more palatable taste and texture that the 21st century is so accustomed to. Combined with low consumption of fibre-rich fruits and vegetables, it is of no coincidence that the UK’s fibre consumption is extremely low – adults and children significantly less than the recommended intake of 30g/day. Fibre is an incredibly important nutrient, and can help to prevent bowel cancer, protect against high cholesterol and reduced the risk of type 2 diabetes – fibre has a low glycaemic index (GI) which means fibre-rich foods allow the slow release of sugars into our body and therefore prevent blood sugar spikes and keep us fuller for longer, and therefore less likely to have additional snacks throughout the day.
Why are we eating these types of foods?
High calorie, processed foods are said to be cheaper than nutritious, fresh high quality meat, fruit and vegetables – although this is highly disputed by various stakeholders [9, 10]. Other factors that may explain the increased consumption of these foods is that they often require less preparation, which is importance for consumers looking for convenience in busy working lifestyles and also for those who have poor food preparation skills.
However, with the majority of the population now overweight or obese in the UK, we have to look past the individual choices in our diet and consider what is going on around us and how this may be influencing what we eat.
Millions of pounds of money is poured into the marketing of unhealthy food and drink in the UK every year. Industry don’t spend this kind of money just for kicks. There is convincing evidence to suggest exposure to advertising of unhealthy food and drink can influence our preferences, consumption habits and also weight status [11]. In addition to this, consumption of sugar-sweetened beverages, living sedentary lifestyles, promotions on unhealthy food and drink products and other environmental influences play a key part in the growing trend of obesity – and therefore increasing the likelihood of consuming energy-dense, nutrient poor diets which could lead to deficiencies in essential vitamins and minerals.
On a more positive note, this growing body of evidence highlights a potential additional benefit of reducing obesity in that it may also reduce the prevalence of nutritional deficiencies in the population. Policymakers and public health should consider the potential nutritional inadequacies of the obese population when providing primary care and treatment, but also strategies to prevent obesity and nutritional deficiencies in the future.
References:
[1] Public Health England (2018) National Child Measurement Programme [online]. Available at: https://fingertips.phe.org.uk/profile/national-child-measurement-programme [Accessed: 25th July 2018]
[2] Public Health England (2018) Severe obesity in 10 and 11 year olds reaches record high [online] Available at: https://www.gov.uk/government/news/severe-obesity-in-10-to-11-year-olds-reaches-record-high [Accessed: 25th July 2018].
[3] Public Health England (2018) Local Authority Health Profiles [online] Available at: https://fingertips.phe.org.uk/profile/health-profiles [Accessed: 25th July 2018]
[4] WHO. Obesity and Overweight. http://www.who.int/mediacentre/factsheets/fs311/en/ [Accessed: 25th July 2018].
[5] Astrup, A and Bugel, S (2018). Overfed but undernourished: recognising nutritional inadequacies/deficiencies in patients with overweight or obesity. International Journal of Obesity. https://doi.org/10.1038/s41366-018-0143-9
[6] Vimaleswaran, K.S., Berry, D.J., Lu, C., Tikkanen, E., Pilz, S., Hiraki, L.T., Cooper, J.D., Dastani, Z., Li, E., Houston, D.K., Wood, A.R., Michaelsson, K and Hypponen, E. (2013). Casual relationship between obesity and vitamin D status: bi-directional mendelian randomisation analysis of multiple cohorts. PLOS Medicine. https://doi.org/10.1371/journal.pmed.1001383
[7] Scientific Report of the 2015 Dietary Guidelines Advisory Committee. United States Department of Health and Human Services; United States Department of Agriculture: Washington, DC, 2015.
[8] Cutler DM, Glaeser EL, Shapiro JM (2003). Why have Americans become more obese? Journal of Economy Perspectives. 17, pp.93–118.
[9] Insitute of Economic Affairs (2017) Cheap as chips [online] Available at: https://iea.org.uk/publications/cheap-as-chips-is-a-healthy-diet-affordable/ [Accessed: 25th July 2018].
[10] Overseas Development Institute (2015) The rising cost of a healthy diet [online] Available at: https://www.odi.org/sites/odi.org.uk/files/odi-assets/publications-opinion-files/9580.pdf [Accessed: 25th July 2018].
[11] Boyland, E. (2017) Junk food marketing: the evidence [online] Available at: http://obesityhealthalliance.org.uk/wp-content/uploads/2018/02/Junk-Food-Marketing-Evidence-Briefing-FINAL.pdf [Accessed: 25th July 2018].
