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Why too much abdominal fat is bad for my health?

Did you know that not every overweight or obese individual is at increased risk of diabetes and heart disease? Many studies over the last 30 years have shown that too much abdominal fat (the fat located in your abdomen) increases the risk of diabetes and heart disease whether or not you are obese or normal weight. This is because abdominal (belly) fat behaves differently than the fat in your hips and thighs. Hip and leg fat is designed to store energy, protecting the other tissues and organs, while abdominal fat is very active and releases fats and other substances that disrupt numerous body functions. If you have too much fat in your abdominal cavity (this is often called intra-abdominal fat or visceral fat), you may be normal weight but "viscerally" obese and thus at high risk of diabetes or heart disease.

Why is intra-abdominal fat bad? First, this fat behaves differently than the subcutaneous (under your skin) fat located in your hips and thighs. It releases fat molecules into the blood that accumulate in other tissues such as the liver, heart and your muscles, impairing their normal function. Second, intra-abdominal fat is loaded with cells (macrophages) that play a role in inflammation and release numerous substances ("adipohormones" or adipokines) that increase your risk of diabetes and heart disease. Third, it has also been suggested that too much belly fat is a sign that your body does not store excess energy from fat in its proper location (i.e., subcutaneously). This causes fat to build up at undesirable locations (such as your heart, your liver, muscles and pancreas) and cause a range of health problems. Thus, abdominal obesity is frequently the cause of complications such as type 2 diabetes, cardiovascular diseases, atherogenic dyslipidemias (disorders in the transport of fat and cholesterol in the blood), liver steatosis (fat accumulation in the liver), sleep apnea and some forms of cancers. Because you can be normal weight and still have too much abdominal fat, physicians and health professionals worldwide must take action to assess this new, hidden risk factor, which has been called the "cholesterol of the 21st century."

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How can I measure how much abdominal fat I have?

On this webpage, the International Chair on Cardiometabolic Risk provides a step-by-step video on how to self-measure your waist circumference. Numerous studies have shown that measuring abdominal waist circumference is the best, simplest way to estimate how much abdominal fat you have. However, you have to know how to interpret measurement results in order to determine whether they indicate high-risk abdominal obesity. Based on the relationship with body mass index (BMI) threshold values for overweight (25 kg/m²) or obesity (30 kg/m²), organizations such as the National Cholesterol Education Program-Adult Treatment Panel III (NCEP-ATP III) have proposed waist circumference values of 102 cm for men and 88 cm for women [1]. These values correspond to a BMI of 30 kg/m² (obesity). However, BMI is limited as it cannot be used to establish valid waist cutoffs to predict potential additional risk. Furthermore, age and ethnicity affect the relationship of waist circumference to intra-abdominal fat and related health risk. For instance, we know that Asians are more prone to diabetes for a given waistline and that this phenomenon may be partly due to the fact that Asians are more likely to store intra-abdominal fat than Caucasians. In addition, African Americans are more likely to store fat subcutaneously than Caucasians. A single cutoff of 102 cm in men and 88 cm in women may therefore be unsuitable for defining excess abdominal fat in all populations worldwide.

An International Diabetes Federation (IDF) committee on the metabolic syndrome attempted to address this problem in its 2005 guidelines. The following table (Table 1) summarizes IDF waist circumference values according to ethnicity and gender. However, these values have not been validated against "hard" clinical outcomes and therefore provide "ballpark" figures to patients and their treating physicians.

This table has been endorsed by the recent Canadian guidelines on obesity, which have also emphasized that waist measurement is a vital sign that needs to be assessed in clinical practice [3]. But, as mentioned above, men, women and various populations differ in their susceptibility to store abdominal fat and in their relationship to diseases. Waist circumference values used to define abdominal obesity should therefore be gender and population specific.

References

1. Executive Summary of The Third Report of The National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation, And Treatment of High Blood Cholesterol In Adults (Adult Treatment Panel III). JAMA 2001; 285: 2486-97.
2. Alberti KG, Zimmet P and Shaw J. The metabolic syndrome--a new worldwide definition. Lancet 2005; 366: 1059-62.
3. Lau DC, Douketis JD, Morrison KM, et al. 2006 Canadian clinical practice guidelines on the management and prevention of obesity in adults and children [summary]. CMAJ 2007; 176: S1-13.

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What to do with my waist measurment?

If your waistline is below the values presented in the table, you are probably not abdominally obese and do not have this new risk factor for diabetes and cardiovascular disease. However, if your waistline is above the values for your gender and ethnic group, you should contact your physician for a proper assessment of your risk factors and overall health.

If your waistline is above the values presented in Table 1, this does not automatically mean that you are abdominally obese. You doctor will evaluate your global health and run simple tests to verify whether you have abnormalities that are commonly called the metabolic syndrome. The metabolic syndrome can be diagnosed by primary care physicians (Table 2) and is most often caused by poor eating habits and a sedentary lifestyle that lead to abdominal fat accumulation and insulin resistance (the cells of your body do not respond normally to insulin). You cannot diagnose the metabolic syndrome by yourself. So if you think that your waistline puts you at risk, please see your physician. Prevention is key. Invest in your health!

For patients diagnosed with excess abdominal fat and the metabolic syndrome, improving their nutritional habits and increasing their levels of physical activity/exercise are the cornerstones of treatment. Measuring waist circumference also provides a good indicator of the amount of abdominal fat loss in response to healthy eating and increased physical activity. In fact, some sedentary men with abdominal obesity may lose abdominal fat and increase their muscle mass through healthy nutrition/physical activity without necessarily losing weight! Losing waist without losing weight is not uncommon in individuals who take steps to change their sedentary lifestyle by incorporating regular physical activity/exercise. In this regard, several sections of our website provide basic tips to help you be more active and eat better. Regular physical activity is probably the best “polypill” available to reduce your risk of diabetes and heart disease. If you think that your waistline is high, see your doctor, take action to invest in your health and quality of life and stay tuned to the website of the International Chair on Cardiometabolic Risk!