We tend to associate malnutrition with being underweight due to hunger and starvation. In fact, although this is indeed the case, obesity is also a major cause of malnutrition in the UK
64% of UK adults are obese, according to the latest government statistics, a figure that has increased from 52.9% since 1993. Obesity is also a major problem in children, affecting around 20% of children by the age of 5 and 23% by age 11
Isn’t malnutrition associated with being underweight?
We tend to associate malnutrition with being underweight due to hunger and starvation. In fact, although this is indeed the case, obesity is also a major cause of malnutrition. Research shows that micronutrient (vitamin and minerals) deficiency is more common in those with a raised BMI than in those of the same age and sex who are not obese.
Malnutrition in the UK is on the rise
The Sunday Times reported that around 11,000 people were admitted to hospital in the UK last year with malnutrition, with doctors reporting they are now seeing diseases they haven’t seen since Victorian times – for example, scurvy and rickets. However, this is the tip of the iceberg. Most malnutrition in the obese population is unseen and undiagnosed.
Most malnutrition in the obese population is unseen and undiagnosed.
Why are obese people malnourished?
There are many reasons why obese people may actually be malnourished. Here are some explanations below.
Too much calorie-dense food with a low nutrient content
- Obesity is often associated with eating processed and ultra-processed foods which are generally high in fat, sugar and salt. In a 2021 study, two groups of non-obese adults followed either an ultra-processed or a healthy diet for 2 weeks and then groups were swapped over. Participants were allowed to eat as much as they liked. The investigators found that those who ate the ultra-processed food, consumed an additional average of 500 calories a day. They also gained around 1 Kg in the 2 weeks while on the ultra-processed diet but lost around 1 Kg on the healthy diet.
- Ultra-processed foods are any foods that have been modified to make them taste better or have a longer shelf life. They include cakes, biscuits, pastries, sweets, chocolate, crisps, ice cream, fruit yoghurts, instant foods, sauces, ready meals, chicken nuggets, burgers, hot dogs, pizza, pies, preprepared pasta, soups and desserts.
- On average, 54% of calories from the UK diet are made up of processed foods. These foods typically have lower nutrient content than unprocessed foods. This might be because the outer casing has been stripped – for example, with refined grains. It may be because the food has been heated to high temperatures before cooking or canning/bottling/freezing, destroying much of the nutritional content. Additives are then incorporated, such as emulsifiers, flavourings, colourants and preservatives all of which can cause food allergies, irritation to the GI tract, and exacerbate symptoms of irritable bowel syndrome (IBS). Some food additives are believed to be carcinogenic.
- Processed foods are typically made with lower-quality ingredients and are cheaper to buy than fresh alternatives. They are often bought in bulk and are seen as a good option for those shopping on a budget or needing to feed a family.
Making poor dietary choices
- Most people do know how to eat healthily – they just don’t or can’t do it. For some, this may be because their lives are so busy and processed food is quick and convenient. But many are tempted by the attractive packaging and clever marketing techniques of convenience foods. Stress and anxiety fuel emotional eating – comfort eating – a time when we crave certain foods, usually fast foods (processed foods) high in fat, carbs and salt.
- Stress levels in the UK at present are at an all-time high. When we regularly eat these types of foods, we lose our natural appetite for fresh fruit and veg and tend to continue to feed off the unhealthy processed options – it becomes a vicious spiral.
Living on a low income
- Undoubtedly not being able to afford food is a major problem which has worsened in the current cost of living crisis. Wage stagnation and the relentless increase in food prices have put more people than ever into food poverty. Understandably, people would rather eat processed food than go hungry because they can’t afford fresh food alternatives. Food banks have seen unprecedented demand, with many people reportedly living off tea and toast and skipping meals.
- The soaring cost in energy costs has left many people unable to switch on the oven or the hob.
Those suffering from disabilities, physical and mental health difficulties
- Some people may be confused about what is healthy and what isn’t. Shopping and physically obtaining the food can be difficult for those who are disabled, or live a long way from the shops and have no transport.
- Fuel, bus and taxi fares are now more expensive, adding to the cost of getting the food home. Poverty is a major cause of stress and anxiety, and quick convenience food can be an easy solution. Those with learning disabilities are known to be at higher risk of malnutrition.
- Over 2 million UK residents live with chronic disease, and this is set to increase as the elderly population continues to rise. 54% of people aged 65 and older already have 2 or more chronic diseases – including heart disease, type-2 diabetes and dementia. A strong link has been established between weight gain and obesity and chronic diseases, as well as thirteen different types of cancer.
Food is less nutritious than it used to be
- Nutritionists are concerned that the protein, vitamin and mineral content of fruit and vegetables has been declining in recent years. For example, in one 2022 Australian study, the iron content of sweet potato, cauliflower, green beans, peas and chickpeas had declined by 30% – 50% in the past 20 years.
- Other studies have had similar findings. This is thought to be because the methods used to irrigate, fertilise and harvest crops now damage the soil, and because of rising levels of CO2 due to climate change.
How does obesity cause malnutrition?
The reasons obesity causes malnutrition are complex and interconnected.
Obesity causes micronutrient deficiencies
Recent research has identified many micronutrient deficiencies which occur as a result of obesity. A high-fat diet is associated with a lower intake of many vitamins – Vitamins A, C, D, E, B1, B9 and B12. These are summarised below:
- Vitamin A
- Vitamin A plays an important role in fat metabolism. Research shows that those with a higher BMI tend to have lower levels of vitamin A. Also that low vitamin A levels may be a consequence of obesity, and obese people may have higher requirements for vitamin A than non-obese.
- Vitamin C
- Vitamin D
- Vitamin D deficiency occurs in 57%-94% of those who are obese. The reasons are not fully understood, but adipocytes(fat cells) tend to ‘hang on’ to vitamin D rather than releasing it into the blood circulation. Those who are obese tend to do less exercise and are exposed to less sunlight, therefore having less vitamin D activation in the kidney and liver. Vitamin D supplements are highly recommended but have not been shown to aid weight loss.
- Vitamin E
- Vitamin E may play a role in body weight. In a 2021 cross-sectional study of 4014 teenagers, girls with higher vitamin E levels had the lowest risk of obesity. Vitamin E is another powerful antioxidant and may be useful, especially in those who are obese with metabolic syndrome.
- Vitamin B1
- Vitamin B1 (thiamine) deficiency has been found in up to 29% of patients asking for bariatric surgery. It may be because high-sugar foods do not usually contain thiamine, and the metabolism of high-sugar foods requires a large amount of thiamine.
- Vitamin B9
- Vitamin B9 (folate) levels are lower in those with obesity. It’s not clear whether folate deficiency can contribute to obesity but research in mice shows this may be the case. Folate-deficient mice fed a high-fat diet had an accumulation of fat cells and a higher production of the hormone leptin.
- Vitamin B12
- B12 deficiency has been found in 10.6% of those with morbid obesity. Low B12 levels are linked to a slowdown in the metabolic rate. It can also result in increased lipogenesis (fat deposition) and insulin resistance.
- Iron
- Iron deficiency anaemia is also more common in those who are obese. For example, in one 2016 study of 619 women aged 20-49 years, iron deficiency was present in 23.5% of those with normal weight, 41.9% of those who were overweight, and 45.6% of those who were obese.
- Recent studies have shown that levels of the hormone hepcidin are elevated in those with obesity. This hormone is central to iron homeostasis. It blocks the intracellular transport of iron and down-regulates genes responsible for the absorption of iron in the intestines resulting in lower iron concentration in the blood. Obesity also causes systemic inflammation which further exacerbates iron deficiency.
Obesity causes long-term damage to the gut-barrier
- The gut epithelial cells usually have tight junctions in between them, allowing the passage of nutrients and water, but keeping out toxins and unwanted metabolites. Studies have shown that in obesity, these junctions become weakened, and this protective effect is lowered. The process is not completely understood but is closely governed by the type of gut bacteria that are present.
- Ethanolamine, produced by the cell membrane as a waste product, weakens the cell junctions. Recently studies have shown that favourable bacteria in a healthy microbiome break down ethanolamine maintaining a tight gut barrier, but in obesity, these bacteria are often absent or reduced in number, and this protective effect is lost.
- Unfortunately, this may not be cured by improving the diet because obesity sufferers may have longstanding gut-barrier dysfunction.
Obesity disrupts the microbiome
- Obese subjects have an increase in lipopolysaccharide (LPS) in their intestines which are produced by gut bacteria. LPS causes chronic gut inflammation and intestinal leakage. The type of gut bacteria present in the GI tract appears to play a crucial role in obesity. When normal-weight mice are transplanted with the gut bacteria from obese mice, they become obese.
- Obese mice have a 50% reduction in Bacteroides and a notable increase in Firmicutes. Obese humans have been found to have similar alterations to their microbiome and losing weight can help to redress this imbalance. However, much more research is needed before clear advice can be given.
Obesity alters neurotransmission
- Obese people may not get the same appetite and satiety cues when they eat as those of normal weight. It’s well established that obesity is associated with disturbances in the neurotransmission pathways that govern appetite, hunger and satiety. The GABA, 5-HT and acetylcholine pathways are good examples.
- Research is in its infancy looking at how drugs might help improve these signalling mechanisms and help treat obesity which scientists have suggested could even be a disease of neurotransmission.
Obesity causes oxidative stress
- Obesity causes oxidative stress, and oxidative stress cause obesity.
- Oxidative stress is a dangerous metabolic pathway which occurs as a result of oxidation – the process of producing energy – which is taking place all the time in every cell of our bodies. As a result of oxidation, electrically charged particles called reactive oxygen species (ROS) are produced, which have the ability to damage DNA. ROS are thought to underpin the development of many of the chronic diseases we see today – including obesity.
- Oxidative stress leads to the deposition of white adipose tissue. It also affects appetite and satiety by disrupting neurotransmission and feedback regarding hunger and satiety. Oxidative stress is linked to higher levels of leptin and leptin resistance. Antioxidants obtained from the diet largely from fruit and vegetables are vital for counteracting oxidative stress, but obese subjects tend to have unhealthy diets lacking in antioxidants.
What can a person who is obese do to improve their nutritional status?
Malnutrition carries serious risks to health. Recent research shows that malnutrition significantly increases the risk of a cardiovascular event and dying from it.
Make an appointment with your GP and ask for a nutritional assessment. This may involve keeping a food diary, blood tests, a BMI calculation, and a medical assessment. You will be given advice about diet, weight loss, exercise and the appropriate vitamin and mineral supplements.
Final thoughts, tackling obesity and malnutrition in the UK
Obesity can be a distressing condition. The Royal College of Physicians is calling for obesity to be recognised as a disease – not just a lifestyle factor. There should be no shame or stigma in going for help. As we have seen in this article, the consequences of obesity are profound, leading to a significant risk of malnutrition and its complications.
- Do you know your BMI? Are you in the obese category?
- If so, what could you do to improve your nutritional health today?
For more information
- Medical News Today – Doctors urged to tackle malnutrition in obesity
This piece was written and provided by Dr Deborah Lee, Dr Fox Online Pharmacy
