​Obesity & Overweight in Adults
October 24, 2017
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Obesity in Adults

Obesity is a growing problem in most countries and is responsible for a significant degree of morbidity and mortality in the world. There are several facets to the problem of obesity:

The prevention of obesity.

The correction of obesity.

The population-based approach.

The individual approach.

Prevention is better than cure and easier. The population-based approach is very important but the doctor in his or her surgery will have to cope with the individual.

Understanding Obesity

The global health guidelines recommend the use of body mass index (BMI) to assess overweight and obese individuals. It advises the measurement of waist circumference to supplement this in individuals with a BMI under 35 kg/m It’s advised that BMI be used as a practical measure of adiposity, but warns that this should be interpreted with caution, as it is not a direct measure. Particular caution should be taken in interpreting BMI in certain groups


In adults, the diagnosis of obesity is most commonly made using BMI level. BMI is calculated as weight in kilograms (kg) divided by height in metres squared (m).

Ideal BMI is 18.5 to 24.9 kg/m The following classification is advised :

A BMI of 25-29.9 kg/m is overweight.

A BMI of 30-34.9 kg/m2 is obese (Grade I).

A BMI of 35-39.9 kg/m2 is obese (Grade II).

A BMI of ≥40 kg/m2 is obese (Grade III) or morbidly obese, meaning that weight is a real and imminent threat to health.

There are a few exceptions that are worthy of note:

A person who is very muscular will have a great weight in muscles and bone to support the muscles and so may have a high BMI without an excess of fat.

In people of Asian origin, risk factors are of concern at a lower BMI.

Waist circumference

Waist circumference in men:

<94 cm is defined as low risk.

94 to 102 cm is defined as high risk.

>102 cm is defined as very high risk.

Waist circumference in women:

<80 cm is defined as low risk.

80 to 88 cm is defined as high risk

>88cm is defined as high risk.

Waist circumference should be used in combination with BMI to assess health risk in those individuals with a BMI <35 kg/m2, ie in overweight or obese grade 1 individuals, as follows.

In overweight individuals (BMI 25-29.9 kg/m):

Low waist circumference confers no increased health risk.

High waist circumference confers an increased health risk.

Very high waist circumference confers a high health risk.

In obese individuals Grade 1 (BMI 30-34.9 kg/m):

1.Low waist circumference confers an increased health risk.

2.High waist circumference confers a high health risk.

3.Very high waist circumference confers a very high health risk.


From 2012 figures, 24% of men and 25% of women are obese. This had increased from 13% and 16% respectively since 1993. A further 42% of men and 32% of women were overweight. This means most adults are overweight or obese. The health and financial implications of this have triggered government and public health policies to attempt to reduce the trend. This increasing trend was seen globally.

Several factors have now been shown to predict the development of obesity in individuals, such as a family history of obesity, lifestyle, diet and socio-economic factors. Prevalence is higher where there is deprivation and in individuals with lower levels of educational achievement.

Genetic factors

There is increasing awareness of an element of genetic influence on obesity. The possibility of determining this opens the potential of effective interventions in the future. The mapping of the human genome, combined with evidence from single-gene mutation cases and animal cross-breeding experiments, have identified a significant link between genetic factors and obesity. It is emerging that obesity is the result of a complex pathophysiological pathway involving many factors that control adipose tissue metabolism. Cytokines, free fatty acids and insulin all play a part and genetic defects are likely to have a significant effect on the fine balance of this process.

KRS2 is one gene that has recently been identified as being implicated in obesity and metabolic rate. DNA sequencing in over 2,000 obese individuals identified multiple mutations of the KRS2 gene, and mutation carriers exhibited severe insulin resistance and a reduced metabolic rate. It may be that modulation of KSR2-mediated effects may have the potential to have therapeutic implications for obesity.


Opportunities to measure height and weight include routine health checks, checks for those with diabetes and cardiovascular disease. It may be a related problem for the patient with diabetes, coronary heart disease, osteoarthritis or snoring


Broaching the subject

Obesity is a clinical condition, with health implications, rather than a criticism about the way a person looks.

Assess for comorbidity: diabetes, hypertension, cardiovascular disease, dyslipidaemia, sleep apnoea, osteoarthritis.

Social history, including diet, exercise, occupation, smoking. Family history, including history of obesity, diabetes, heart disease.

Medication which may aggravate weight gain

Oral hypoglycaemic agents, especially sulfonylureas and thiazolidinediones (“glitazones”) – so use metformin first-line. (Insulin when used in the management of type 2 diabetes can also aggravate weight gain.)

Antidepressants including tricyclics, mirtazapine, monoamine-oxidase inhibitors.

Anticonvulsants, particularly sodium valproate, gabapentin, vigabatrin.

Antipsychotics, especially the atypical antipsychotics amisulpride, aripiprazole, clozapine, olanzapine, quetiapine and risperidone.



Beta blockers Pizotifen

Progestogen-only contraceptive injections.

Conditions that may affect weight

  1. Hypothyroidism
  2. Crushing’s syndrome
  3. Growth hormone deficiency
  4. Polycystic ovary syndrome
  5. Hypothalamic damage
  6. Genetic syndromes associated with hypogonadism


Assess risk factors by measuring lipids and HbA1c.

In addition, a few other investigations may be required, as indicated by history and examination:

Hormone profile including sex hormones and cortisol. Hormonal causes of obesity are rare and cortisol may be slightly elevated simply by obesity.

TFTs – hypothyroidism is a rare cause of obesity and does not cause gross obesity. Other investigations, as suggested by comorbidities – eg, ECG, CXR.

Risks of obesity

A meta-analysis found that Grades II and III of obesity were associated with significantly higher all-cause mortality.

The risks are just averages and risks increase with increasing obesity.

Relative increased risk of diseases in obesity
Disease Relative risk for women Relative risk for men
Type 2 diabetes 12.7 5.2
Hypertension 4.2 2.6
Myocardial infarction 3.2 1.5
Cancer of the colon 2.7 3.0
Angina pectoris 1.8 1.8
Gallbladder disease 1.8 1.8
Ovarian cancer 1.7 N/A
Osteoarthritis 1.4 1.9
Stroke 1.3 1.3

Obesity is an important risk factor in the development of chronic respiratory disorders such as chronic obstructive pulmonary disease (COPD), asthma, obstructive sleep apnoea and obesity hypoventilation system.

If the person develops a surgical condition, diagnosis is more difficult and almost every postoperative complication is more frequent, including deep vein thrombosis, chest infection and wound dehiscence. Not only is osteoarthritis more common but treatments such as total hip replacements are more likely to be problematical in obesity.

Obesity increases the risk of breast cancer. It also increases the risk of carcinoma of the endometrium . Polycystic ovary syndrome is usually associated with obesity, as is stress incontinence. Obesity impairs fertility, especially in the female.

Obesity increases the risk of fatty liver, along with other features of the metabolic syndrome. Fatty liver, now the most common cause of liver disease, affects up to 90% of obese individuals. One study suggests that type 2 diabetes may be associated with an increase in visceral fat mass (ie abdominal fat) as opposed to general adiposity.

Benefits of weight loss

Health benefits associated with weight loss include:

Improved lipid profiles.

Reduced disability from osteoarthritis.

Lower all-cause mortality as well as specifically lower diabetes-related mortality and cancer-related mortality.

Reduced risk of diabetes. Improved diabetic control. Reduced blood pressure.

Improved lung function in people with asthma.

One study of people with type 2 diabetes showed that weight loss of 5-10% of body weight improved the chances of achieving:

A 0.5% drop in HbA1c.

A 5 mm Hg drop in diastolic blood pressure.

A 5 mg/dL increase in HDL level.

A 40 mg/dL drop in triglyceride level.

A more significant weight loss of 10-15% was associated with greater improvements.


There is no quick fix. The World Health Organization sees obesity as a chronic disease. Management is not simply helping to shed some unwanted weight but a long-term approach to change attitude, habits and values for the rest of that person’s life.

General points

Multicomponent strategies are required. Which interventions to use should be tailored to the individual and their preferences, health, past history, level of risk, comorbidity and social circumstances.

Interventional strategies to consider are dietary modification, physical activity, behavioural interventions, pharmacological interventions and surgery.

This includes weight loss targets of 0.5-1 kg (1-2 lb) per week, healthier eating and increased physical activity.

Overview of management of different categories of obesity


Low waist circumference – general advice on healthy weight and lifestyle.

High or very high waist circumference – structured advice regarding diet and exercise.

Comorbidities – structured advice on diet and activity; consider drug treatment after evaluating the effect of lifestyle changes.

Obese (I)

No comorbidities – structured advice regarding diet and exercise.

Comorbidities – structured advice on diet and activity; consider drug treatment after evaluating the effect of lifestyle changes.

Obese (II)

No comorbidities – structured advice on diet and activity; consider drug treatment after evaluating the effect of lifestyle changes.

Comorbidities – structured advice on diet and activity; consider drug treatment after evaluating the effect of lifestyle changes. Consider surgery.

Obese (III)

Structured advice on diet and activity. This may need to be via a specialised weight management programme.

Consider drug treatment after evaluation of lifestyle changes.

Consider surgery.

Diet and exercise

Aim for both dietary modification and the initiation of exercise. Losing weight without exercise is very difficult. This is one reason for early intervention, before exercise is severely limited by morbid obesity, coronary heart disease, severe COPD, severe osteoarthritis or other such diseases that prevent physical exertion. The initial aim should be towards a daily 600 kcal deficit of energy requirements through change in dietary habits and exercise.


The first problem may be to convince the patient that he or she is eating too much. It is important to explain to the patient that the equation about calories in and calories out has no exception. It may be helpful to ask the patient to keep a food diary, including all snacks and drinks taken.

There are many different approaches to dieting; be flexible to find the one that suits the individual.

There is not currently any evidence that one type of commonly undertaken diet programme is more effective or more safe than any other.

Health guidelines recommend that diets should be undertaken with expert support and intensive follow-up; that health professionals delivering advice should undertake specific training, and work within multidisciplinary teams.

NICE guidelines of 2014 recommend diets with a 600 kcal deficit, or low-fat diets. Avoidance of very restrictive or nutritionally unbalanced diets is also advised, as these are ineffective in the long term. Stress the other health benefits of eating a healthy diet.

Low-calorie diets (800-1600 kcal per day) may be considered, but health guidelines point out they may be nutritionally incomplete. Very low-calorie diets (under 800 kcal per day) should not be used routinely.

They should not be undertaken for more than 12 weeks.

The long-term aim is a balanced healthy diet.


Value of exercise – this is more than just the calories expended in the session. It tends to increase basal metabolic rate and, after vigorous exercise, metabolism is stimulated for the next 36 hours. It is now known to reduce the risk of diabetes and cardiovascular disease. It also helps people to feel good about themselves.

Realistic expectations – people who are obese may have done no exercise for many years. It is important to discuss the options to find something appropriate and sustainable. It must also be something that the individual will enjoy; otherwise, he or she will not persevere. An over-ambitious programme is doomed to failure. An inadequate programme will confer no benefit.

Expert advice – guidelines suggest that adults should be encouraged to do 30 minutes of moderate-intensity activity, either as one session or in bouts of 10 minutes, on at least five days a week. To prevent obesity, most people would need to do 45-60 minutes of moderate-intensity exercise every day, particularly if calorie intake is not adjusted. For those who have been obese and lost weight, 60-90 minutes per day are advised to avoid relapse.

Behavioural interventions

Behavioural interventions require the support of a suitably trained professional. Strategies advised include:

Self-awareness of behaviour and progress.

Stimulus control.

Goal setting.

Slowing of the rate of eating.

Exploring and involving social support.

Problem solving.


Cognitive restructuring (modifying thoughts).

Reinforcing changes.

Relapse prevention strategies.

Strategies for dealing with weight regain.

There is little evidence on which eating behaviours can be addressed and remedied with psychological treatments. There is currently little evidence for efficacy of behavioural therapies.

Pharmacological management

General points

Anti-obesity medication should only be considered after diet, behavioural changes and exercise have been tried and evaluated. If the patient’s weight has reached a plateau despite these measures, or if targets have not been achieved, pharmacological treatment may be considered.

Pharmacological treatment may be used to maintain weight loss, rather than continue to lose weight. .

Vitamin and mineral supplements should be considered, particularly for vulnerable groups like the elderly and growing adolescents.

Those with type 2 diabetes may lose weight at a slower rate and appropriate allowance should be made.

Regular review of adverse effects and to reinforce lifestyle advice is important.

People being withdrawn from anti-obesity medication should be offered support because it is at this time that their self-confidence and belief in their ability to make changes may be low.


Action – orlistat is a lipase inhibitor which acts by reducing the absorption of dietary fat. It prevents absorption of around 30% of dietary fat.

Effectiveness – orlistat significantly increases weight loss compared to placebo but its effectiveness is limited by its side-effects. Clinical trials suggest a moderate weight loss compared to placebo – about 2-5 kg over a year. There is also a small but significant reduction in total cholesterol, the ratio of total cholesterol to high-density lipids and systolic and diastolic blood pressure. Most patients gain weight after stopping treatment but trials suggest it takes three years to gain weight lost in one year on the drug.

Indications – individuals with a BMI of 28 kg/m2or more in the presence of significant comorbidities(eg, type 2 diabetes, high blood pressure, hyperlipidaemia) OR a BMI of 30 kg/m2 or more with no associated comorbidities. These individuals should be on a mildly hypocaloric, low-fat diet.

If on long-term therapy,monitor A, D, E and beta-carotene levels and prescribe supplementation if appropriate. If vitamin supplements are required, these should be taken at least two hours after an orlistat dose, or at bedtime. Additional contraception may be needed in women experiencing marked gastrointestinal side-effects (eg, diarrhoea). Underlying kidney disease may result in hyperoxaluria and oxalate nephropathy.

Common problems: abdominal discomfort/distension, liquid oily stools, faecal urgency andincreased frequency, flatulence – more so if a diet contains 2000 kcal/day and is high in fat. Other common problems include headaches, upper respiratory tract infections and hypoglycaemia. Less frequently, rectal pain, menstrual irregularities, anxiety, and fatigue occur.

Rare side-effects: rare reports of hepatitis and cholelithiasis. Warn people to stop orlistatand seek medical advice if symptoms such as jaundice, itching, dark urine or abdominal pain develop.


International health guidelines place a greater emphasis on the role of bariatric surgery in the management of obesity. Guidelines advise it is an option where the following criteria are all fulfilled:

BMI 40 kg/m2 or more, or between 35 kg/m2 and 40 kg/m2 with other significant disease (for example, type 2 diabetes or high blood pressure) that could be improved if they lost weight.

It is advised that people who have developed type 2 diabetes mellitus within the preceding ten years, and have a BMI of 35 kg/m should be offered an expedited assessment for bariatric surgery. Also those people with type 2 diabetes and a BMI of 30-34.9 kg/m should be assessed for surgery, and offered the option where appropriate.


Obesity is associated with decreased life expectancy. Excess morality is greater with increasing obesity and with earlier age of onset. For those who are obese, any loss of weight is beneficial and, within reason, the more the better; most of the complications of obesity can be reduced by weight loss.