Treating obesity: lifestyle measures, drugs and bariatric surgery
Established obesity is treated in steps: diet, physical activity and behavioural change come first, anti-obesity drugs and bariatric surgery are considered for people whose weight puts their health at risk, and each step has its own benefits, harms and limits of evidence.
Lifestyle measures
Diet, physical activity and behavioural changes remain the first-line treatment for overweight and obesity, but these measures may not be sufficient to promote a clinically significant and sustained weight loss in morbidly obese people. The most successful programmes for long-term weight control combine diet, physical activity and behaviour modification. Physical activity is recommended as a component of weight management for preventing weight gain, for weight loss and for preventing weight regain after weight loss. An American College of Sports Medicine position stand recommended moderate-intensity physical activity of 150–250 minutes a week to prevent weight gain, and stated that at least 250 minutes a week are necessary for clinically significant weight loss and for weight maintenance after weight loss. In observational studies, people who successfully maintained a large weight loss for at least a year typically engaged in about seven hours a week of moderate- to vigorous-intensity exercise.
Popular diets
Diets vary in their scientific evidence and efficacy, and also in their use and popularity according to personal preferences and vogue. According to Medical News Today, the eight most popular diets in 2009 were:
- the Atkins diet: low-carbohydrate, high-protein, high-fat
- the Zone diet: 40% carbohydrates, 30% fats and 30% proteins in every meal
- the vegetarian diet
- the vegan diet
- the Weight Watchers diet: a points system, exercise and a support network
- the South Beach diet: low-glycaemic-index products, whole grains, specific fruits and vegetables, olive oil and lean protein sources
- the raw food diet: foods and drinks that are not processed, are completely plant-based and are ideally organic
- the Mediterranean diet: plant foods, fruits, beans, nuts, cereals, seeds, olive oil, cheese and yogurts, moderate amounts of fish and poultry, up to four eggs a week, small amounts of red meat, and low to moderate amounts of wine
The British Dietetic Association's list of the ten most popular commercial diets in 2011 was:
- the Dukan diet: low-carbohydrate, high-protein, restricted vegetables and fat
- the Atkins diet
- the Cambridge diet: meal replacement products
- the South Beach diet
- the Slimming World diet: low-fat foods and a support network
- the Slim-Fast diet: meal replacement products
- the LighterLife diet: meal replacement products and weekly counselling
- the Weight Watchers diet
- the Rosemary Conley diet: a low-fat, low-glycaemic-index diet and regular exercise
- the Jenny Craig diet: one-to-one support, a meal delivery service and tailored exercise plans
Sustaining weight loss
Losing weight is difficult because it requires a whole change in behavioural patterns, to which people are usually resistant. Regaining weight as soon as one returns to normal eating habits after a fad diet is extremely frustrating. Losing weight and keeping it off over the long term requires modifying one's diet and engaging in regular physical activity, so maintaining a new weight needs sustained change.
Candidates for drugs or surgery
Depending on the extent of overweight, some people may need additional medical treatment, particularly when their physical or psychological health is seriously compromised, for instance when they are unable to engage in physical activity. These patients, at increased medical risk because of their weight, may be considered for drug therapy or bariatric surgery, but they should ideally first have tried to lose weight through dieting and physical activity without success.
How anti-obesity drugs act and why they were withdrawn
Anti-obesity drugs act through one of three mechanisms: suppressing appetite, increasing the body's metabolism (its caloric expenditure), or impairing the digestion and absorption of nutrients such as fat. Amphetamines were banned from diet pills in 1979. A number of anti-obesity drugs have been launched and then withdrawn from the market because of safety concerns, including these:
- aminorex, withdrawn in 1972 because of pulmonary hypertension
- fenfluramine and dexfenfluramine, withdrawn in 1997 because of case reports of heart valve disease and pulmonary hypertension
- rimonabant, withdrawn in 2008 because of increased risks of depression and suicidal ideation
- sibutramine, withdrawn in 2010 because of increased risk of heart attacks and strokes
In the years up to 2012, new anti-obesity drugs entered the market in a recurring cycle, only to be withdrawn when their side effects emerged.
Side effects of anti-obesity drugs
Anti-obesity drugs may cause serious and life-threatening side effects, and these are often inherent to their mechanism of action, so caution is recommended in prescribing and using any of them. Stimulants, for instance, increase heart rate and blood pressure and cause restlessness and insomnia. One of the main problems with anti-obesity drugs is that the neurological basis of appetite, and how to modulate it, is not fully understood, because so many hormones and neurotransmitters are involved in eating and in generating and processing satiety signals. Likewise, many parameters control the storage, bioavailability and expenditure of energy that keep anabolism and catabolism in balance.
Approved anti-obesity drugs and their limits
As of 2012, the drugs approved by the US Food and Drug Administration (FDA) for short-term weight loss, of up to 12 weeks, were the appetite suppressants phentermine, diethylpropion and phendimetrazine and the newcomer lorcaserin. People taking them usually lose 5 kg more than they would without medication, with the maximum effect within the first six months. The only anti-obesity drug the FDA had approved for long-term use, of less than a year, was the lipase inhibitor orlistat (Xenical), approved in 1999 and available over the counter in the USA since 2007. Some antidepressants, such as bupropion, the anticonvulsants topiramate and zonisamide, and the antidiabetic drugs metformin, exenatide and pramlintide were used off-label against overweight, and were being studied in more detail for their benefit against obesity.
Anti-obesity drugs are not a practical long-term solution for people who are chronically overweight or obese. They are generally approved only for people with a BMI of at least 30, or a BMI of at least 27 with an obesity-related condition such as hypertension, type 2 diabetes or dyslipidaemia. The anti-obesity drugs available in 2012 also had limited efficacy.
Bariatric surgery procedures
Bariatric (weight loss) surgery, an option for extremely obese people, achieves weight loss by reducing the size of the stomach with an implanted, adjustable device (gastric banding), by removing a portion of the stomach (sleeve gastrectomy, or biliopancreatic diversion with duodenal switch), or by resecting the small intestine and re-routing it to a small stomach pouch (gastric bypass). Gastric bypass is considered the gold standard in the USA, where 140,000 procedures were performed in 2005, and its most common form is the Roux-en-Y gastric bypass.
Weight loss after bariatric surgery
Bariatric surgery is scientifically proven to reduce weight in moderate and severe obesity more successfully than conventional treatments. Because of the anti-obesity drugs' cycle of launch and withdrawal, it remained in 2012 the most successful treatment for moderate and severe obesity. It allows loss of up to 50 kg by reducing the size of the stomach and the levels of ghrelin, the hormone that causes hunger, that the stomach produces. The smaller stomach constrains the daily amount of food taken and requires a thorough change of dietary patterns after surgery, because overeating causes nausea and vomiting. The resulting reduction in the absorptive surface of the small intestine may make supplementation with minerals and vitamins necessary, often for life.
Effects of bariatric surgery on co-morbidities
In most morbidly obese patients, bariatric surgery resolves major obesity-related co-morbidities, including type 2 diabetes, hypertension, dyslipidaemia, metabolic syndrome, non-alcoholic fatty liver disease, nephropathy, left ventricular hypertrophy and obstructive sleep apnoea. Through these effects, bariatric surgery appears to reduce cardiovascular morbidity and mortality. It also brings significant improvements in quality of life.
Who is considered for bariatric surgery
The US National Institutes of Health recommend bariatric surgery for people with a BMI of at least 40, or a BMI of at least 35 with serious co-morbidities. The American Diabetes Association recommends it only for adults with a BMI over 35 and type 2 diabetes, especially if the diabetes or its associated co-morbidities are difficult to control with lifestyle and drug therapy. Its 2012 Standards of Medical Care in Diabetes state that gastric reduction surgery, either gastric banding or procedures that bypass, transpose or resect sections of the small intestine, can be an effective weight loss treatment for severe obesity, and that US national guidelines support its consideration for people with type 2 diabetes and a BMI over 35. Where all else fails, bariatric surgery may be considered for people with a BMI of at least 35 who are at increased health risk. Evidence available in 2012 suggested that bariatric surgery could be appropriate for people with a BMI of 35–40 and no co-morbidities, or a BMI of 30–35 with significant co-morbidities, further expanding the number of patients who could be considered for it.
Diabetes outcomes after bariatric surgery
The American Diabetes Association's 2012 Standards of Medical Care in Diabetes state that bariatric surgery has been shown to lead to near or complete normalisation of glycaemia in 55–95% of diabetes patients, depending on the procedure. A meta-analysis of bariatric surgery studies involving 3,188 patients with diabetes reported remission of diabetes, meaning normalisation of blood glucose levels in the absence of medications, in 78%, and the remission rates were sustained in studies with follow-up longer than two years. Weight loss and diabetes remission rates were higher with procedures that bypass portions of the small intestine than with those that only constrict the stomach. The meta-analysis and other studies suggest that intestinal bypass procedures may have glycaemic effects independent of their effects on body weight, perhaps involving the incretin axis, the hormones that increase insulin release.
In a study published in 2010 of 110 patients with type 2 diabetes and a mean BMI of 47, Roux-en-Y gastric bypass resulted in a mean loss of excess weight of 63% at one year and 84% at two years. Diabetic medication was discontinued in 68% of those patients and reduced in a further 14%.
Two single-centre studies published by 2012 that compared bariatric surgery with conventional medical therapy in obese diabetic patients reported greater weight loss, better glycaemic control and reduced use of medicines for co-morbid conditions in significantly more patients in the surgical groups. One of them reported that these effects were independent of pre-operative BMI and post-operative weight loss.
Complications and mortality of bariatric surgery
Rates of morbidity and mortality directly related to bariatric surgery had been reduced considerably in the years up to 2012. In a systematic review and meta-analysis published in 2007, total mortality was 0.28% within 30 days and 0.35% from 30 days to two years. Mortality depended on the type of procedure, open or laparoscopic and restrictive or malabsorptive, on the surgeon's experience and on the patient's pre-operative health. The most common post-operative complications include gastric dumping syndrome (bloating and diarrhoea after eating), anastomotic and staple-line leaks, hernia, infections, pulmonary events and haemorrhage. Morbidity is lower after laparoscopic procedures, which make up the largest proportion of bariatric operations. Longer-term concerns include vitamin and mineral deficiencies, hypocalcaemia, osteopaenia, osteoporosis, hyperparathyroidism, gallstones, renal diseases and, rarely, Wernicke's encephalopathy and hypoglycaemia resulting from insulin hypersecretion.
Long-term evidence on bariatric surgery
In line with the rising incidence of obesity and reflecting improvements in surgical technique, the number of bariatric operations performed worldwide was rising exponentially in 2012. Compared with non-surgical interventions, bariatric surgery appears to be clinically effective and cost-effective for moderately to severely obese people. However, the studies available in 2012 on whether bariatric surgery reduces long-term morbidity and mortality by curing or preventing the onset of chronic diseases were limited, and generally difficult to conduct because of several confounders. More effort is required to monitor its long-term safety and efficacy, particularly for quality of life and overall life expectancy, for instance by setting up large patient registries and following patients for longer. The pros and cons of each procedure must be weighed carefully for each person in view of its short- and long-term benefits and risks.