Obesity and weight gain

Summary

Obesity levels in the UK are rising and by 2020 eight out of 10 men and almost seven in 10 women could be overweight or obese. Being overweight increases the risk of diabetes, high blood pressure, heart disease and several different types of cancer.

The body has a natural tendency to store fat, so if you eat lots of fatty foods like meat, dairy foods, cake and biscuits, you gain weight. Even lean cuts of meat contain relatively high fat levels compared to plant foods. Chicken is not the answer as modern supermarket chickens contain more fat than protein! Just one meal from KFC (or McDonalds) can contain more fat than you should eat in an entire day. It took filmmaker Morgan Spurlock 14 months to lose the 11kg he gained eating at McDonalds three times a day for a month.

The NHANES study found that those who eat the most meat are around 30 per cent more likely to be obese and have central obesity (a fat tummy), which increases the risk of diabetes.

People who eat meat tend to consume more calories than vegetarians and vegans. However, the EPIC-PANACEA study found that even when they eat the same number of calories, meat-eaters gain more weight. They also found that people who eat lots of protein, at the expense of fat or carbohydrate (containing fibre), gain more weight too. Both results put the theory behind the Atkins diet in a dim light!

Research from 170 different countries shows that meat intake is directly linked to weight gain. Another study suggesting that meat is as bad as sugar found that if we eat more than enough food, fats and carbohydrates are digested first for energy and the energy in meat protein (not combined with fibre like plant protein) ends up being stored as fat. They say that public health strategies should be put in place to reduce meat consumption.

There is a wealth of research showing how a low-fat vegan diet can help achieve and maintain healthy weight. See The Incredible Vegan Health Report at: www.vivahealth.org.uk for more details.  

Around two-thirds of adults and a third of children in the UK are overweight. Of these, one in every four adults and around one in every five children (aged 10-11), are obese – the UK has become the ‘fat man of Europe’ (NHS Choices, 2015d). The UK has the highest level of obesity in Western Europe, ahead of France, Germany, Spain and Sweden. Obesity levels in the UK have more than trebled in the last 30 years. In 2010, a team of experts, led by Professor Klim McPherson at Oxford University, predicted that by 2020, eight out of 10 men and almost seven in 10 women will be overweight or obese (Brown et al., 2010). By 2050, more than half the population could be obese. McPherson’s study says this would lead to a 23 per cent rise in the prevalence of obesity-related stroke, a 34 per cent rise in obesity-related high blood pressure, a 44 per cent rise in obesity-related heart disease and a 98 per cent rise in obesity-related diabetes.

Being overweight increases the risk of a range of health problems including diabetes, high blood pressure and up to ten different types of cancer. It can also impair a person’s well-being, quality of life and ability to work. Compared with a healthy weight man, an obese man is:

  • five times more likely to develop type 2 diabetes
  • three times more likely to develop bowel cancer
  • more than two and a half times more likely to develop high blood pressure – a major risk factor for stroke and heart disease

An obese woman, compared with a healthy weight woman, is:

  • almost 13 times more likely to develop type 2 diabetes
  • more than four times more likely to develop high blood pressure
  • more than three times more likely to have a heart attack

NHS Choices, 2015d.

McPherson says: “We are being overwhelmed by the effects of today’s ‘obesogenic’ environment, with its abundance of energy-dense food and sedentary lifestyles”.

Research has shown that we have a natural tendency to store fat – it’s a survival mechanism that helped early humans survive famine and food shortages. However, a wide variety of foods are now available in abundance and it can be tempting to overeat and to go for unhealthy types of food – high in sugar and fat.

Most unhealthy saturated fat in the average UK diet comes from: fatty cuts of meat, poultry skin, meat products such as sausages and pies, whole milk and full fat dairy products, coconut oil and palm oil, pastry, cakes and biscuits, sweets and chocolate. The government recommends eating less of these foods and more foods containing unsaturated fats such as avocados, nuts, seeds, plant-based oils and spreads. 

Somehow, chicken continues to slip under the net in many health studies that focus on red and processed meat. This does not mean it is a healthy option. Some researchers have suggested that people who replace red meat with chicken do so in an attempt to improve their health. These people are also less likely to smoke, consume less alcohol and take regular physical exercise. These lifestyle patterns may mask the harmful effects of white meat that would be more apparent otherwise.

Poultry now accounts for nearly half of all the meat bought in the UK; British people are currently eating an estimated 2.2 million chickens per day. But is it really a healthy option? Would you be better off replacing chicken with chickpeas? Is chicken as low in fat as we have been led to believe? Professor Michael Crawford, of London Metropolitan University, found that modern organic and non-organic broiler chickens sold for human consumption provide more energy from fat than from protein (Wang et al., 2010). This is not common knowledge!

In 1976, the Royal College of Physicians and the British Cardiac Society recommended replacing fatty red meat with poultry because it was considered to be lean and therefore lower in fat than other meats. However, the situation has changed drastically since then, with a striking increase in fat content of the standard broiler chicken (that’s the common type of bird sold in supermarkets). Professor Crawford set out to put the record straight and provide a snapshot of data on fat in chickens now sold to the public. Crawford’s team collected samples between 2004-2008 from UK supermarkets and farm shops. They measured the fat content and found that the chickens they sampled contained more fat than protein! (Wang et al., 2010). They concluded that in view of the obesity epidemic, chickens that provide several times the fat energy compared with protein seem illogical and said this type of chicken husbandry needs to be reviewed with regard to its implications for animal welfare and human nutrition.

There are growing concerns about health impacts of the increasing consumption of so-called fast foods and takeaway foods on health, of which chicken nuggets, wings and drumsticks play an increasing role. A 2015 review of the evidence found that frequent consumption of fast foods is accompanied with overweight and abdominal fat gain, impaired insulin and glucose balance, lipid and lipoprotein disorders, induction of systemic inflammation and oxidative stress increasing the risk of diabetes, metabolic syndrome and cardiovascular disease (Bahadoran et al., 2015).  

Chemical analyses of 74 samples of fast-food menus consisting of French fries and fried chicken (nuggets/hot wings) bought in McDonalds and KFC outlets in 35 different countries in 2005-2006 showed that the total fat content of the same menu ranged from 41 to 65g at McDonalds and from 42 to 74g at KFC (Stender, 2007). The government say we should consume no more than 70g of fat a day. So this could be all the day’s fat in one meal! KFC’s own website says that, for example, their Mighty Bucket For One contains 67.3g of fat of which 11.1g is saturated! We’re advised to eat less fat, especially saturated fat. UK health guidelines recommend that the average man should eat no more than 30g of saturated fat a day and the average woman should eat no more than 20g of saturated fat a day.

In the documentary film Super-Size Me, independent filmmaker Morgan Spurlock ate McDonald’s food three times a day for 30 days and gained 11kg (Spurlock, 2004). His cholesterol went up from just over 4mmol/l (a healthy number) to 6mmol/l, he experienced mood swings, sexual dysfunction and fat accumulation in his liver. It took Spurlock fourteen months to lose the weight gained from his experiment using a vegan diet.

It’s not just fast food and takeaway meat products that are causing problems. The National Health and Nutrition Examination Survey (NHANES) study looked at associations between general meat consumption and weight among US adults (Wang and Beydoun, 2009). Results showed that those who ate the most meat were around 27 per cent more likely to be obese and 33 per cent more likely to have central obesity compared to those eating the least. This is most likely to be due to their higher energy and fat intake. Indeed, those eating the most meat consumed around 700 more calories per day than those consuming the least.

Meat intake is related to weight gain because of its high energy and fat content. The more calories you eat, the more weight you gain. However, one of the largest nutrition studies ever, the European Prospective Investigation into Cancer and Nutrition-Physical Activity, Nutrition, Alcohol, Cessation of Smoking, Eating Out of Home and Obesity (EPIC-PANACEA) project, found that meat consumption was significantly associated with weight gain and the link remained even after controlling for calorie intake (Vergnaud et al., 2010).

They investigated the link between total meat, red meat, poultry and processed meat and weight gain over five years among a total of 103,455 men and 270,348 women aged 25-70, recruited  from 10 European countries. Results confirmed meat consumption was associated with weight gain in both men and women, no surprises there. However, an intake of 250g meat per day (≈450 calories) would lead to an annual weight gain of nearly half a kilogram more than the weight gain experienced by someone eating a diet containing the same number of calories but with a lower meat content! After five years the weight difference would be 2kg. The strongest link with annual weight change was observed for poultry. However, when subjects with previous illness and those likely to lie about their diets were excluded, the association of weight gain with poultry dropped and the strongest link was seen with processed meat.  

These results contradict the theory behind high-protein diets (such as the Atkins diet) that suggest eating lots of meat and animal protein makes you feel full and want to eat less and so helps you lose weight. The result are however in agreement with most previous studies that show a positive link between meat intake and weight gain suggesting a decrease in meat consumption can help weight management.

The EPIC-PANACEA study was challenged by a group of scientists (one whom serves on a speaker’s bureau for the National Cattlemen’s Beef Association). They suggested the additional weight gain in the meat-eaters may have been muscle mass and said the study should have assessed body composition by measuring body fat (Astrup et al., 2010). A number of the EPIC-PANACEA team responded repeating the analyses in a smaller group of their study including 91,214 people (Vergnaud et al., 2010a). They measured their waists as an indicator of abdominal fat. In agreement with their original finding, they found that meat consumption was positively associated with an increase in waist circumference (0.76cm increase after five years for every 100 calorie increase in daily meat intake). They acknowledged the usefulness of assessing body composition to address further the association between meat and weight gain. The National Cattlemen’s Beef Association did not respond.

It’s unclear why meat-eaters appear to gain more weight than people eating the same number of calories but with less or no meat. The EPIC-PANACEA analysis accounted for differences in BMI, physical activity, educational level, smoking status, total energy intake and plausible misreporting. They did suggest a theory; if meat-eaters acquire all detrimental lifestyle features and if the sum of all these together is more than the sum of each individual effect, this could account for the results seen.

Other studies show how meat intake meat is associated with higher fasting glucose and insulin concentrations, which promotes the absorption and conversion of glucose into either glycogen or fat (Fretts et al., 2015). How the consumption of meat may influence glucose and insulin levels is still open to speculation; it may be to do with NOCs in processed meat or formed within the body, which have a toxic effect on pancreatic beta cells and promote diabetes. Haem iron, advanced glycation end products and amino acids (eg leucine), may also influence pancreatic beta cell function, insulin secretion and the pathogenesis of diabetes. The point is, meat impairs glucose metabolism and makes people fatter than people eating the same number of calories but without the meat.

The EPIC-PANACEA study team also found that diets containing high levels of protein, at the expense of fat or carbohydrate, were also positively associated with weight gain, especially when they missed out on carbohydrates that are rich in fibre (Vergnaud et al., 2013). Those eating diets with more than 22 per cent of energy from protein had a 23-24 per cent higher risk of becoming overweight or obese compared to those eating diets with no more than 14 per cent of energy from protein. So high-protein diets are not advisable for weight loss. It has been suggested that in addition to restricting calories, a possible reason Atkin’s dieters lose weight is that because their diet is so monotonous, they tend to eat smaller amounts of food when allowed fewer food choices in the meal (Astrup et al., 2004). A bit like the study suggesting that cider vinegar might help with weight loss because it makes people feel nauseous! (Darsi et al., 2014).   

Research analysing data from 170 different countries resulted in an important finding in two papers (You and Henneberg, 2016; You and Henneberg, 2016a). After adjusting for factors such as people’s activity levels, income, lifestyle and calorie consumption, meat intake was directly and significantly linked to excess weight. In fact, meat turned out to be as bad as sugar and these two food groups together explain almost all the variation in people’s body weights. Both studies describe why and how meat is linked to obesity. If we eat more than enough food, the fats and carbohydrates are digested first and supply all the energy we require. Meat protein is digested later and the body only needs to use a small proportion of it so most of the energy it provides is surplus to requirements and is converted to fat which is then stored in your body. The authors conclude that public health strategies should be put in place to reduce meat consumption.

There is a wealth of research showing how a low-fat vegan diet can help achieve and maintain healthy weight.