Overweight and obesity

Overweight and obesity

Most people know what the term obesity means: an increased body weight caused by the excessive accumulation of fat. Overweight and obesity occur when more calories are taken into the body than are burnt up over time. In other words, if you don’t burn up the energy you consume it will be stored as fat, and over time this may lead to excessive weight gain and obesity. So someone who works in a very physically demanding job, such as a building-site labourer, may need between 4,000 and 5,000 calories per day to maintain their normal weight. Whereas an office worker who drives to work and does not take any exercise may only need 1,500 calories per day (NHS Direct, 2005).  

Another way of defining obesity is to measure your body mass index (BMI). This is your weight in kilograms divided by the square of your height in metres. There are many websites that can do conversions and calculations for you (see Appendix II). In England, people with a body mass index between 25 and 30 are categorised as overweight, and those with an index above 30 are categorised as obese. The Food Standards Agency’s BMI calculator describes 18.5 to 25 as healthy and suggests that a BMI of less than 18.5 is underweight (FSA, 2006). The average BMI of an adult in Africa and Asia falls between 22 and 23, whereas in North America and Europe the average BMI is much higher ranging from 25 to 27 (WHO, 2006d). In 2004 the FSA reported that the number of obese adults in the UK has risen considerably since the last survey in 1987; numbers of obese men have risen from eight per cent to 25 per cent and women from 12 per cent to 20 per cent (FSA, 2004). This survey showed that the level of obesity in men has risen faster than those of women. In addition, the FSA survey reported that 41 per cent of men and 33 per cent of women were found to be overweight.   

The main causes of obesity include an excessive intake of food coupled to a lack of exercise and a sedentary lifestyle. Other much less frequent causes include a genetic predisposition or an underlying illness (such as hypothyroidism). The British Medical Association (BMA) warns that childhood obesity levels have soared in the UK over recent years. In 2002 in the UK, 22 per cent of boys and 28 per cent of girls aged between two and 15 were either overweight or obese (BMA, 2005). The BMA attribute this rise to the fact that children are eating too much for the amount of physical activity they undertake. This is very worrying as early childhood obesity tends to indicate adult obesity which can lead to serious health risks later in life. Obesity is a known risk factor for many illnesses including type 2 diabetes, heart disease, hypertension, stroke, gall bladder disease and certain forms of cancer especially the hormonally related and large-bowel cancers.

The WHO suggests that as the degree of affluence increases, diets high in complex carbohydrates give way to diets high in saturated fats and sugars (WHO, 2006d). This combined with a shift towards less physically demanding work, an increasing use of automated transport, technology in the home and more passive leisure pursuits means that we are less active than our parents and our grandparents.

The WHO suggests several ways to lose weight including eating more fruit, vegetables, nuts and whole grains; engaging in daily moderate physical activity for at least 30 minutes; cutting the amount of fatty, sugary foods in the diet and moving from saturated animal-based fats to unsaturated vegetable-oil based fats (WHO, 2006d). Whole milk, cheese, cream, butter, ice-cream and most other dairy products, apart from skimmed and non-fat products, contain significant amounts of saturated fat and cholesterol. While we do need a certain amount of fat in the diet there is no nutritional requirement for saturated fat. Cow’s milk is high in the unhealthy saturated fats and low in the healthy polyunsaturated essential fatty acids, which are required in the diet for good health. Most people eat much more fat than they need, and making minor changes to the diet (cutting down on fat) can make a big difference over time.

A number of small-scale studies (of less than 35 obese adults) have suggested that the consumption of dairy products may actually help people lose weight (Zemel et al., 2004; Zemel et al., 2005). In these studies Professor Zemel, who has received a considerable amount of funding from the National Dairy Council (COS, 2005), suggests that diets containing calcium from dairy foods might affect fat cell metabolism in such a way that greater weight loss can occur despite an identical calorie intake with a control group not consuming so much dairy. Interestingly, a subsequent study (by a research group including Zemel but not as the first named author) found no evidence that a diet high in dairy products enhances weight loss (Thompson et al., 2005).

Dr Amy Joy Lanou, the nutrition director of the PCRM, warns that care should be taken when interpreting the findings from Zemel’s trials. Furthermore, Lanou suggested that the US National Dairy Council’s claims promoting dairy consumption for weight loss went well beyond Zemel’s findings. Lanou suggests that it was likely that calorie restriction, not dairy consumption, caused the weight loss reported in these studies (Lanou, 2005).

In June 2005 the PCRM decided enough was enough and filed two separate lawsuits to stop the multimillion-dollar advertising campaign claiming that milk facilitates weight loss. The PCRM filed one lawsuit to the US Food and Drugs Administration and the other to the US Federal Trade Commission. In the lawsuit the PCRM charged the National Dairy Council, the International Dairy Foods Association, Dairy Management Incorporated, Dannon Company, Kraft Foods and other dairy manufacturers with purposefully misleading customers (PCRM, 2005).

Despite the dairy industry’s claims, scientific studies show that adding dairy products to the diet does not help control weight; in fact the research confirms that in many cases the reverse is true, consuming milk and dairy foods can lead to weight gain. Some studies designed to test the effects of dairy consumption on weight found no difference in weight between groups consuming relatively large amounts of dairy foods compared to groups consuming little (Lappe et al., 2004; Gunther et al., 2005). Another study, this time of the effects of just calcium supplementation on weight loss in women who had recently given birth, found no relationship between calcium supplementation and weight loss (Wosje, 2004). Researchers at the University of British Columbia in Vancouver, Canada, who reviewed the scientific literature on the effects of dairy products or calcium supplements on body weight found that out of nine studies on dairy products, seven showed no significant difference while two studies linked weight gain to dairy consumption (Barr et al., 2003). Furthermore, out of 17 studies on calcium supplementation, just one reported weight loss.

A recent large scale study that followed over 12,000 children for three years concluded that the children who drank the most milk gained the most weight (Berkey et al., 2005). The analyses showed that out of milk, calcium, dairy fat and total energy intake, it was energy intake that was the most important predictor of weight gain. The authors attribute this weight to… you’ve guessed it, the added calories! To most people it is just common sense, a calorie is a calorie and weight gain or weight loss is a case of mathematics. If you take in more energy (calories) than you use, you will gain weight. If you use up more energy than you consume, you will lose weight. There is no magic bullet, and if there were it seems very unlikely that it would be cow’s milk.