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Metabolic syndrome and diabetes

• What is metabolic syndrome?
• What is insulin resistance?
• How common is metabolic syndrome and what are the causes?
• What are the serious consequences of metabolic syndrome?
• How to manage metabolic syndrome?
  1. Dietary recommendation
  2. Physical activity and exercise
  3. Drug treatment
  4. Weight loss surgery
• Calculation of Body Mass Index (BMI)

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What is metabolic syndrome?

Metabolic syndrome is also known as insulin resistance syndrome or Syndrome X. It consists of 5 main components: obesity, insulin resistance, high blood pressure, abnormal blood lipids, and diabetes.

The diagnosis is based on the 2005 International Diabetes Federation (IDF) consensus as follows:

Central obesity (weight circumference ≥ 94cm for Europid men and ≥ 80cm for Europid women, with ethnicity specific values for other groups

plus any 2 of the following 4 factors

– Triglyceride level ≥ 1.7 mmol/l (150 mg/dl)
– HDL cholesterol < 1.03 mmol/l (40 mg/dl) in males and <1.29 mmol/l (50 mg/dl) in females
– Systolic BP ≥ 130 mmHg or diastolic BP ≥ 85 mmHg
– Fasting plasma glucose ≥ 5.6 mmol/l (100 mg/dl) or previously diagnosed type 2 diabetes

What is insulin resistance?

Insulin resistance is a state in which a given increase in plasma insulin in an affected individual causes less of an effect in lowering the plasma glucose level than it does in a normal individual.

The results of a number of population-based studies have shown that approximately 25% of individuals have insulin resistance. The incidence increases greatly in individuals with type 2 diabetes (from approximately 25% to 85%)

How common is metabolic syndrome and what are the causes?

The estimates of the prevalence of metabolic syndrome in the US and Europe differ depending on the populations studied and the definition applied. The prevalence rate in many western countries is 25-35%. In Singapore it is about 20 – 25% (using Asian population criteria), whereas in the US, 22-23%.

The cause of metabolic syndrome is poorly understood. Insulin resistance is thought to be an underlying feature. Individual features are partially determined by familial factors – obesity, diabetes, hypertension. Lifestyle and culture of inactivity and obesity play an important role. There is also a higher prevalence among older individuals.

People are getting fatter because our ‘leisured society’ is dominated by cars, computers and all manner of labour-saving devices, has led to a reduction in physical activity. This is equivalent to perhaps 500-750 calories per day compared with 50 years ago.

What are the serious consequences of metabolic syndrome?

Overweight and obesity have been associated with type 2 diabetes. Each kilogram increase in weight of the population increases the risk of diabetes by almost 5%. Up to 80% of patients with type 2 diabetes are obese. Furthermore, besity promotes insulin resistance.

In an epidemiological study published in 2001, in patients with metabolic syndrome, compared with normal patients, the risk of coronary heart disease is 2.96 times higher, heart attack 2.63 times, stroke 2.27 times and death 1.81 times.

How to manage metabolic syndrome?

Currently, there are no randomized controlled trials that aim specifically at treating metabolic syndrome. However the main goal of treating metabolic syndrome is to reduce the risk of cardiovascular diseases such as stroke and heart attack, and to reduce the risk of type 2 diabetes.

Management is therefore involved 1) treating the underlying risk factors, e.g. overweight and obesity, physical inactivity and the unhealthy diet., and 2) treating the metabolic risk factors such as high blood cholesterol and triglycerides, high blood pressure and blood glucose.

The most important step is weight reduction. Combined intervention of a calorie-deficit diet, increased physical activity and behavioural treatment is most successful for weight loss and maintenance.

Maintaining a healthy weight needs to be a lifetime goal. World Health Organisation recommends that adults should aim to gain no more than 5kg throughout adult life.

Other components of metabolic syndrome such as high blood pressure, raised blood cholesterol and triglycerides, etc, should be treated accordingly with lifestyle therapy and medications. Target goals for the treatment are shown in the following table:

1. Dietary recommendations

The recommendations for diet composition are similar to the general dietary recommendations, e.g low intake of saturated fats, and cholesterol, and increased intake of fruits, vegetables, and whole grains.

Low carbohydrate diet such as Atkins diet shows short term benefits of lower triglyceride levels, raised HDL-cholesterol levels and reduced body weight. However the long term effects have not been studied adequately.

Irrespective of whatever food intake, restricting calories is what causes weight loss. Therefore low calorie diets i.e. 500 to 1000 kcal/day reduction, are recommended for weight loss in overweight and obese persons. Further calorie reductions have no added advantage. Reducing dietary fat, along with reducing dietary carbohydrates, usually will be needed to produce the caloric deficit needed

2. Physical activity and exercise

It is well known that exercise contributes to modest weight loss. It reduces ‘intra-abdominal fat’ even in those who lost no weight. It has positive effects on high blood pressure and improves insulin sensitivity and thus blood glucose control. The standard exercise recommendation is a daily minimum of 30 minutes of moderate-intensity physical activity.

Calculation of Body Mass Index (BMI)

BMI = weight (kg) / height (m) x height (m)