An association between certain metabolic disorders and cardiovascular disease has been known since the 1940s. In the 1980s, this association became more clearly defined and the term metabolic syndrome (also known as syndrome X or the dysmetabolic syndrome) was coined to designate a cluster of metabolic risk factors that come together in a single individual.
The main features of metabolic syndrome include insulin resistance, hypertension (high blood pressure), cholesterol abnormalities, and an increased risk for clotting. Patients are most often overweight or obese.
Insulin resistance refers to the diminished ability of cells to respond to the action of insulin in promoting the transport of the sugar glucose, from blood into muscles and other tissues. Because of the central role that insulin resistance plays in the metabolic syndrome, a separate article is devoted to insulin resistance. Please see Insulin Resistance article for more information.
The definition of metabolic syndrome depends on which group of experts is doing the defining. Based on the guidelines from the 2001 National Cholesterol Education Program Adult Treatment Panel (ATP III), any three of the following traits in the same individual meet the criteria for the metabolic syndrome:
- Abdominal obesity: a waist circumference over 102 cm (40 in) in men and over 88 cm (35 inches) in women.
- Serum triglycerides 150 mg/dl or above.
- HDL cholesterol 40mg/dl or lower in men and 50mg/dl or lower in women.
- Blood pressure of 130/85 or more.
- Fasting blood glucose of 110 mg/dl or above. (Some groups say 100mg/dl)
The World Health Organization (WHO) has slightly different criteria for the metabolic syndrome:
- High insulin levels, an elevated fasting blood glucose or an elevated post meal glucose alone with at least 2 of the following criteria:
- Abdominal obesity as defined by a waist to hip ratio of greater than 0.9, a body mass index of at least 30 kg/m2 or a waist measurement over 37 inches.
- Cholesterol panel showing a triglyceride level of at least 150 mg/dl or an HDL cholesterol lower than 35 mg/dl.
- Blood pressure of 140/90 or above (or on treatment for high blood pressure).
Metabolic syndrome is quite common. Approximately 20-30% of the population in industrialized countries have metabolic syndrome. By the year 2010, the metabolic syndrome is expected to affect 50-75 million people in the US alone.
As is true with many medical conditions, genetics and the environment both play important roles in the development of the metabolic syndrome.
Genetic factors influence each individual component of the syndrome, and the syndrome itself. A family history that includes type 2 diabetes, hypertension, and early heart disease greatly increases the chance that an individual will develop metabolic syndrome.
Environmental issues such as low activity level, sedentary lifestyle, and progressive weight gain also contribute significantly to the risk of developing the metabolic syndrome.
Metabolic syndrome is present in about 5% of people with normal body weight, 22% of those who are overweight and 60% of those considered obese. Adults who continue to gain 5 or more pounds per year raise their risk of developing metabolic syndrome by up to 45%.
While obesity itself is likely the greatest risk factor, others factors of concern include:
- women who are post-menopausal,
- smoking,
- eating an excessively high carbohydrate diet,
- lack of activity (even without weight change), and
- consuming an alcohol-free diet.
Metabolic syndrome is worth caring about because it is a condition that can pave the way to both diabetes and heart disease, two of the most common and important chronic diseases today.
Metabolic syndrome increases the risk of type 2 diabetes (the common type of diabetes) anywhere from 9-30 times over the normal population. That’s a huge increase. As to the risk of heart disease, studies vary, but the metabolic syndrome appears to increase the risk 2-4 times that of the normal population.
There are other concerns as well that should be mentioned. Metabolic syndrome is associated with fat accumulation in the liver (fatty liver), resulting in inflammation and the potential for cirrhosis. The kidneys can also be affected, as there is an association with microalbuminuria -- the leaking of protein into the urine, a subtle but clear indication of kidney damage.
Other problems associated with metabolic syndrome include obstructive sleep apnea, polycystic ovary syndrome , increased risk of dementia with aging, and cognitive decline in the elderly.
The major goals are to treat both the underlying cause of the syndrome, and also to treat the cardiovascular risk factors if they persist. As has been discussed, the majority of people with metabolic syndrome are overweight and lead a sedentary lifestyle.
Lifestyle modification is the preferred treatment of metabolic syndrome. Weight reduction usually requires a specifically tailored multifaceted program that includes diet and exercise. Sometimes medications may be useful.
Diet
A detailed discussion of diet therapies, pros and cons of various diets etc. is beyond the scope of this article. However, there is now a trend toward the use of a Mediterranean diet -- one that is rich in “good” fats (olive oil) and contains a reasonable amount of carbohydrates and proteins (such as from fish and chicken).
The Mediterranean diet is palatable and easily sustained. In addition, recent studies have shown that when compared to a low fat diet, people on the Mediterranean diet have a greater decrease in body weight, and also had greater improvements in blood pressure, cholesterol levels, and other markers of heart disease -- all of which are important in evaluating and treating metabolic syndrome
Exercise
A sustainable exercise program, for example, 30 minutes 5 days a week is reasonable to start, providing there is no medical contraindication. (If you have any special concerns in this regard, check with your doctor first.) There is a beneficial effect of exercise on blood pressure, cholesterol levels, and insulin sensitivity, regardless of whether weight loss is achieved or not. Thus, exercise in itself is a helpful tool in treating metabolic syndrome.
Cosmetic surgery to remove fat
Some people may ask: "Why not just have liposuction of the abdomen and remove the large amount abdominal fat, which a big part of the problem?" Data thus far shows no benefit in liposuction on insulin sensitivity, blood pressure, or cholesterol. As the saying goes, "If it's too good to be true, it probably is." Diet and exercise are still the preferred primary treatment of metabolic syndrome.
What if lifestyle changes are not enough to treat metabolic syndrome?
What if changes in lifestyle do not do the trick, what then? Drugs to control cholesterol levels, lipids, and high blood pressure may be considered.
If someone has already had a heart attack, their LDL (“bad”) cholesterol should be reduced below 100mg/dl. (Some experts now say it should be under 70mg/dl.) A person who has diabetes has a heart attack risk equivalent to that of someone who has already had one, and so should be treated in the same way. What remains controversial is whether metabolic syndrome should be considered a coronary equivalent or not. If you have metabolic syndrome, a detailed discussion about lipid therapy is needed between you and your doctor, as each individual is unique.
Blood pressure goals are generally set lower than 130/80. Some blood pressure medications offer more than simply lowering blood pressure. For example, a class of blood pressure drugs called ACE inhibitors has been found to also reduce the levels of insulin resistance and actually deter the development of type 2 diabetes. This is an important consideration when discussing the choice blood pressure drugs in the metabolic syndrome.
The discovery that a drug prescribed for one condition, and has other beneficial effects is not new. Drugs used to treat high blood sugar and insulin resistance may have beneficial effects on blood pressure and cholesterol profiles. A class of drugs called thiazolidinediones [pioglitazone (Actos) and rosiglitazone (Avandia)] also reduce the thickness of the walls of the carotid arteries.
Metformin (Glucophage), usually used to treat type 2 diabetes, also has been found to help prevent the onset of diabetes in people with metabolic syndrome. Indeed, in my practice, I routinely discuss metformin with my patients who have metabolic syndrome. Many of my patients who have insulin resistance associated with metabolic syndrome opt for metformin therapy. However, there are currently no established guidelines on treating metabolic syndrome patients with metformin if they do not have overt diabetes.
The term “metabolic syndrome” is a way of identifying individuals at high risk for the development of heart disease and diabetes. Intuitively we all know that obesity, high cholesterol, and hypertension are bad omens. We also know that insulin resistance precedes type 2 diabetes, and can itself be an important condition meriting treatment. Everyone reading this article knows someone who is overweight, hypertensive, or has cholesterol levels that are “a little high.” It may be a brother, sister, parent, neighbor, or even yourself.
The main point, is to treat the risk factors as bad things, before worse things happen. And while these changes can be addressed at a doctor’s office, the other 99.999% of the time, they need to be addressed in the real world. We need to start having healthier food options readily available. We need to have time during the day to take a walk. We need to be aware of our own heath, and to make whatever changes we can to improve it.
The final take home message is:
- Find a walk or exercise buddy.
- Take a walk during your work break, even if it is just around the building.
- Go to a health food store.
- Look at what you feed your kids.
- Urge them to get outside and play.
