Brisk Walking Benefits People with Metabolic Syndrome

Metabolic syndrome is the term used to describe the group of medical disorders that commonly precede development of cardiovascular disease and type-2 diabetes. Cardiovascular disease and type-2 diabetes are leading causes of premature death in people with metabolic syndrome.

The five recognized components of metabolic syndrome – elevated blood pressure, high fasting blood glucose, raised blood triglycerides, reduced HDL cholesterol and abdominal obesity – occur together more often than would happen by chance alone. Therefore, physicians classify individuals displaying at least three of the five disorders at the same time as having metabolic syndrome.

Since no single medication is available to treat metabolic syndrome, physicians customize individualized treatment plans by prescribing medications specific for each primary medical disorder. There is a strong body of evidence that increased physical activity improves the individual disorders associated with metabolic syndrome – reduces blood pressure for example – in people without metabolic syndrome. Thus, advice to increase physical activity while reducing caloric intake has become a major strategy for the treatment of metabolic syndrome.

While the advice on lifestyle changes in the treatment of metabolic syndrome is common, the question of whether increased physical activity benefits people with metabolic syndrome to the same extent it does for those without metabolic syndrome requires further study. Another unanswered question is whether more physically active lifestyles reduce the risk of early death in those with metabolic syndrome.

A recent study examined this question in more than 50,000 adults, 27 percent of whom had metabolic syndrome at the start. Participants were assigned to one of four activity categories – inactive, low, moderate and high – based on detailed questionnaires completed at the start of the study. Low activity was equivalent to the energy required for brisk walking.

The study revealed that each level of increased physical activity reduced early death equally whether or not the individual had metabolic syndrome, particularly for those below the age of 65. The study also showed that the risk of early death from any cause, but especially from cardiovascular disease, decreased as the level of physical activity increased in both men and women with metabolic syndrome. While the risk of premature death continued to lessen as activity level increased, the greatest reduction in premature death was observed between those who were inactive and those with low activity levels.

Significance: Most individuals, whether or not they have metabolic syndrome, are able to walk quickly. A level of physical activity equivalent to brisk walking benefits those with metabolic syndrome to the same extent it benefits individuals without metabolic syndrome. Even minimal amounts of physical activity are beneficial for achieving healthy lifestyles.

Citation: “Even low level of physical activity is associated with reduced mortality among people with metabolic syndrome, a population based study (the HUNT 2 study, Norway).” D Stensvold, J Nauman, TIL Nilsen et al. BMC Medicine, October 2011

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Glycemic Index – Inaccurate Predictor of Actual Blood Glucose Response

Blood glucose levels are lowest when we wake, and then increase and decrease after we eat. Different foods influence how much blood glucose levels fluctuate throughout the day. Glycemic Index (GI) is a mathematical summary of the rise and fall in blood glucose measured after an individual food is eaten.

By definition, foods with a high GI ranking cause blood glucose levels to increase the most. Conversely, foods with a low GI ranking cause blood glucose levels to increase the least. Discrete GI values have been determined for hundreds of individual foods.

However, when we eat a meal we consume a mixture of foods, not a single food. Thus, a formula using the GI of the individual foods that are part of an actual meal has been developed to estimate the possible blood glucose response to that meal. Numerous clinical studies have compared the blood glucose response to a meal predicted by this formula and to that actually measured after the meal had been eaten. Some clinical studies report poor agreement between predicted and actual blood glucose response, whereas other studies report good agreement.

A recent study examined the agreement between measured and predicted GI values. The blood glucose response to three different meals was measured in 30 healthy adults. The actual blood glucose response of each individual was then compared to the blood glucose response that the standard formula would predict for the same study participant.

The main finding was calculated blood glucose responses significantly overestimated actual blood glucose responses. Not only did the standard formula overstate actual blood glucose responses to the test meals, the extent of these overestimations was variable. For example, the GI of the potato meal was 22% lower than the GI predicted by the formula. The formula predicted that the GI of the spaghetti meal would have been 50% higher than the actual blood glucose response.

Significance: This study expands the evidence that consumption of meals, and thus multiple-food diets, affects blood glucose response in ways that cannot always be predicted by calculation. Study authors caution the research community and healthcare professionals to be aware of the unreliability of using published GI values to predict the actual blood glucose response to a specific meal. These findings point out that blood glucose response is more complex than simplistic advice to base dietary advice on a single mathematical concept.

Citation: "Calculating meal glycemic index by using measured and published food values compared with directly measured meal glycemic index." H Dodd, S Williams, R Brown and B Venn. American Journal of Clinical Nutrition, October 2011

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