Being overweight can lead to obesity, a medical condition in its own right, but also a risk factor for many of the fatal diseases in the UK, including heart disease, high blood pressure, and cancer.
Obesity is the most prevalent nutritional disorder in prosperous communities, a marked change from primitive society when there was no such plentiful supply of appetising food.
The journey from being overweight to obese can occur unnoticed if the weight gain is gradual, but with every small increase in body fat, longevity decreases.
Data from insurance companies indicate that an obese person is 2-3 times more likely to die prematurely than their lean counterparts.
So when do you move from being to overweight to being obese?
Obesity is diagnosed when the Body Mass Index (BMI) is over 30 kg/m2. There are two classes of obesity.
Severity of obesity Moderate obesity Grade II 30-40 kg/m2 Severe obesity Grade III Above 40 kg/m2 |
Besides the BMI, a waistline of more than 120 cm (47 inches) for men, and more than 88 cm (34 inches) for women represents a significant health risk
A waist:hip circumference ratio of 0.95 or more for men and more than 0.85 for women indicates central obesity - abdominal fat distribution. Above this ratio, there is an increased risk of cardiovascular disease and diabetes.
The health risks
Obesity causes physical, psychological and social risks to health. Physical effects are mechanical, due to the effect of the mass of extra tissue on the functioning of the systems and organs, and changes in metabolism. It increases the risk of illness, in particular cardiovascular disease, diabetes, and osteoarthritis.
Cardiovascular disease
Obesity increases the risk of heart disease, hypertension, stroke and thrombosis. Obese women have a threefold increase in the risk of having a heart attack.
The heart has to work harder to pump blood around the body in obese people, becoming enlarged. The increased force of pumping blood raises blood pressure.
In addition, the tendency of obese people to consume a high-fat diet raises cholesterol and blood lipid levels, further increasing the risk of heart disease. Adipose tissue acts as a reservoir for cholesterol.
Diseases and conditions precipitated by obesity
| Disease / Condition | Proposed Reason for Increased Risk |
| Hormone-sensitive cancers e.g. breast, uterine, cervical, ovarian, prostatic. | Increased body fat, increased production of aromatase, the enzyme which converts testosterone to oestrogen. |
| Diabetes | Higher circulating levels of insulin, which promotes fat production and storage. |
| Osteoarthritis | Greater strain and increased wear and tear on joints. |
| Sleep apnoea | Excess abdominal fat presses on the diaphragm, causing problems with the supply of blood to lungs, resulting in episodes of breathing cessation during sleep. |
| Gallstones | Increased adipose causes increased cholesterol storage. Excess cholesterol in the bile, then stored in the gall bladder, increases the risk of infections and gallstones. |
| Kidney stones and kidney failure | Failure is due to hypertension (increased plasma uric acid) |
| Predisposition to prolapse | Due to increasing pressure in the abdomen. |
| Respiratory difficulties | Excess abdominal fat pressing on the diaphragm, stopping efficient blood flow to the lungs. |
| Increased risk during operations | Greater risk during all stages - the anaesthetic, the procedure, and post-operative recovery. |
Metabolic and endocrine changes commonly found in obese people are the consequence of nutritional disorder, not the cause. The cause, in the vast majority of cases, is the taking in of more energy from food than is expended. This is discussed in the Overweight section.
Metabolic changes common in obesity - Glucose tolerance decreases
- Sensitivity to insulin decreases
- Plasma insulin increases
- Plasma cholesterol increases
- Plasma triglycerides increase
- Sensitivity to growth hormone decreases
- Plasma uric acid increases
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Due to the health risks associated with obesity, people should consult a doctor or dietician for effective treatment and management. Prevention and cure can only occur by treating the patient's way of life.
Weight loss
In addition to diet, exercise and behavioural therapy, obese people often require very low calorie diets under medical supervision, medication, or surgery. Weight loss of as little as 5-10% can lead to significant health improvements in obese people, such as reducing blood pressure and cholesterol.
The challenge to find a diet that works for you can be frustrating and distressing, and poor treatment with repeated weight gain and loss (yo-yo diet) may be more harmful than none.
The weight cycle is often caused through crash diets, whereby food intake is drastically reduced to the point of health risk. Such measures go against everything required from a slimming diet as the body proceeds into survival mode, reducing Basal Metabolic Rate (BMR) so reducing energy expenditure.
The dangers of crash diets 1) Nutrient deficiencies e.g. calcium and iron, leading to osteoporosis and anaemia respectively 2) Excessive loss of lean muscle tissue as protein is diverted for use as an energy source 3) Depression and eating disorders through preoccupation with weight control |
Very low calorie diets
Under medical supervision, very low calorie diets (VLCDs) can be safe and effective for obese people, but they are not appropriate for the general population.
VLCDs are based on a calorie intake of less than 800 kcal/day, to result in a rapid, short-term weight loss. The general weight loss is 2-3 times greater than conventional diets. VLCDs should be used in conjunction with exercise and behaviour modification, to promote weight maintenance thereafter.
The diets are available in liquid formulas, the most successful being those based on a moderate carbohydrate and moderate protein content. Supervision is required to ensure the diet is balanced, providing all of the essential vitamins and minerals, and supplements may be required.
Health monitoring
It is important for people to appreciate the health benefits achieved through even small amounts of weight loss. Observations of blood pressure, blood sugar, or mobility improvements may help to encourage continuation of treatment, whether it be via diet and exercise alone or medical assistance.
Medicines
There are four main classes of medicine suitable for treating obesity: appetite suppressants, fat blockers, bulk-forming agents, and thyroxine.
Appetite suppressants e.g. Sibutramine and Duramine
The effectiveness of these prescription-only drugs is short term only, as once the medication has ceased, appetite returns to normal. They act as psychomotor stimulants, stimulating higher corticol centres, helping overcome fatigue and depression. They should not be used for more than 12 weeks, and they increase blood pressure and heart rate - so are likely to be unsuitable for people already suffering from hytpertension and cardiovascular disease.
Fat blockers e.g. Orlistat (Xenical)
Xenical inhibits lipase, the enzyme involved in fat digestion, allowing up to 30% of the fat content of the diet to pass through the gut, to be excreted rather than stored. Long-term use can reduce the absorption of fat soluble vitamins.
Bulk-forming agents e.g. Celevac
These expand in the stomach, imparting a feeling of fullness, so reducing consequent food intake.
Thyroxine
The delivery of the hormone thyroxine stimulates metabolism. It is contraindicated except where obesity is associated with hypothyroidism.
Surgery
Obesity treatment through surgical means is rare in the UK. The operations carry risk and side effects are not uncommon.
Surgical options include those that interfere with the gastrointestinal tract so decreasing food intake. The operation that by-passes the small intestine is a jejunoileostomy, which carries a 4% risk of mortality.
The operation that decreases stomach size is known as a gastroplasty, which reduces its capacity to 60ml.
Jaw wiring physically prevents the consumption of solid foods. Other possibilities include liposuction, lipectomy, and abdominoplasty.
Fat removal is only effective at removing small specific areas in order to sculpt a particular area of the body.
20/05/2009