Dietary control
This largely depends on a reduction in calorie intake
The most common diets allow a daily intake of approximately 4200 kJ (1000 kcal), although this may need to be nearer 6300 kJ (1500 kcal) for someone engaged in physicalwork.
Very low calorie diets are also advocated by some, usually over shorter periods of time, but unless they are accompanied by changes in lifestyle, weight regain is likely. Patients must realize that prolonged dieting is necessary for large amounts of fat to be lost. Furthermore, a permanent change in eating habits is required to maintain the new low weight.
It is relatively easy for most people to lose the first few kilograms, but long-term success in moderate obesity is poor, with an overall success rate of no more than
10%.
Many dietary regimens aim to produce a weight loss of approximately 1 kg per week. Weight loss will be greater initially owing to accompanying protein and glycogen breakdown and consequent water loss. After 3–4 weeks, further weight loss may be very small because only adipose tissue is broken down and there is less accompanying water loss.
Patients must understand the principles of energy intake and expenditure, and the best results are obtained in educated, well-motivated patients. Constant supervision by healthcare professionals, by close relatives or through membership of a slimming club helps to encourage compliance.
It is essential to establish realistic aims. A 10% weight loss, which is regarded by some as a ‘success’ is a realistic initial aim.
An increase in exercise will increase energy expenditure and should be encouraged – provided there is no contraindication since weight control is usually not achieved without exercise.
The effects of exercise are complex and not entirely understood. However, exercise alone will usually produce little long-term benefit. On the other hand there is evidence to suggest that in combination with dietary therapy, it can prevent weight being regained. In addition, regular exercise (30 min daily) will improve general health.
The diet should contain adequate amounts of protein, vitamins and trace elements. A diet of 4200 kJ (1000 kcal) per day should be made up of more than 50 g protein,
approximately 100 g of carbohydrate, and 40 g of fat. The carbohydrate should be in the form of complex carbohydrates such as vegetables and fruit rather than simple sugars.
Alcohol contains 29 kJ/g (7 kcal/g) and should normally be discouraged. It can be substituted for other foods in the diet, but it often reduces the willpower. With a varied diet, vitamins and minerals will be adequate and supplements are not necessary.
A balanced diet, attractively presented, is of much greater value and safer than any of the slimming regimens often advertised in magazines.
Most obese people oscillate in weight; they often regain the lost weight, but many manage to lose weight again. This ‘cycling’ in bodyweight may play a role in the development of coronary artery disease.
A wide range of diets are available, including low-fat or low-carbohydrate diets, and some suit certain individuals better than others. The following general statements can be made about them.
All low-calorie diets produce loss of bodyweight and fat,
irrespective of dietary composition. Short-term weight
loss is faster on low-carbohydrate diets, as a result of
greater loss of body water, which is regained after the
end of dietary therapy.
■ Very low-fat diets are often low in vitamins E, B12, and zinc. Very low carbohydrate diets may be nutritionally inadequate, and may lead to deficiencies.
■ Low-fat diets decrease LDL triglycerides and increase HDL, whereas low-carbohydrate diets produce a greater decrease in HDL and triglyceride, with no change in LDL.
■ There are some potential long-term concerns with low-carbohydrate diets (high in fat and protein), including increased risk of osteoporosis, renal stones and atheroma (due to high saturated fat, high trans fat and cholesterol and the lack of fruits, vegetables and whole grains), but long-term studies are lacking.
■ Low-energy-density diets, often bulky and rich in fibre and complex carbohydrates, may be more satiating butthey are often less palatable than high-energy-dense
diets which may affect long-term compliance.
■ Liquids, e.g. soft drinks, appear to be less satiating than solid foods.
■ A recent study has shown that Mediterranean and lowcarbohydrate diets are as effective as a low-fat diet for weight loss.
Drug therapyDrugs can be used in the short term (up to 3 months) as an adjunct to the dietary regimen, but they do not substitute for strict dieting.
Centrally acting drugs:■ Drugs acting on both serotoninergic and noradrenergic pathways, e.g. sibutramine, tesofensine.
■ Cannabinoid-1 receptor blockers, e.g. rimonabant (now withdrawn due to depression/suicide risk), acting on the endocannabinoid system.
■ Drugs acting on the noradrenergic pathways do suppress appetite but all have been withdrawn in the UK because of cardiovascular side-effects.
Peripherally acting drugs:■ Orlistat is an inhibitor of pancreatic and gastric lipases. It reduces dietary fat absorption and aids weight loss. Weight regain occurs after the drug is stopped. It has been used continuously in a large-scale trial for up to 2 years. The patients complain of diarrhoea during treatment and to avoid this take a low-fat diet resulting in weight loss.
■ Incretins. Glucagon-like peptide 1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) are being used in type 2 diabetes mellitus.
They suppress appetite and are being used in obesity
Surgical treatmentSurgery is used in some cases of morbid obesity (BMI > 40 kg/m2) or patients with a BMI > 35 kg/m2 and obesity-related complications, after conventional medical treatments have failed.
A variety of gastrointestinal surgical procedures have been used. They fall into two main groups:
■ restrictive procedures, which restrict the ability to eat
■ malabsorptive procedures, which reduce the ability to absorb nutrients
A systematic analysis of bariatric surgical procedures concluded that, in comparison to non-surgical treatments, they produced significantly more weight loss (23–37 kg), which was maintained to 8 years and associated with improvement in quality of life and co-morbidities.
■ Roux-en-Y gastric bypass. This procedure incorporates both restrictive and malabsorptive elements (gastrojejunostomy). This procedure, like other malabsorptive
procedures, may result in nutrient deficiencies requiring careful long-term follow-up.
■ Bilio-pancreatic diversion (including the duodenal switch variation). This is another malabsorptive procedure that requires long-term evaluation.
■ Laparoscopic adjustable gastric banding. This is a restrictive procedure, in which a band is placed around the upper stomach to produce a small proximal pouch and a large distal remnant. It has a perioperative mortality of < 0.5%, and results in loss of about 60% (43–78%) of the excess weight after 3 years, although longer-term follow-up studies are required.
Laparoscopic adjustable gastric banding has been reported to produce greater weight loss and fewer sideeffects (e.g. vomiting) and operative revisions than vertical banded gastroplasty.
■ Liposuction. The removal of large amounts of fat by suction (liposuction) does not deal with the underlying problem and weight regain frequently occurs. There is no reduction in cardiovascular risk factors.
