Benign obesity – does it matter where you have fat?

There are a number of studies that show the impact of obesity on the human skeleton, organs and functioning of the body. Many have linked obesity with a variety of cancers and listed the restrictions, such as impeded pulmonary function, that comes with excess weight. Further, insulin sensitivity decreases as weight increases. Increased weight also increases metabolic disorders.

Wildman and colleagues examined 6036 adults in the NHANES cohort. This is the National Health and Nutrition Examination Survey. Adults with a history of underweight or cardiovascular disease were grouped as normal weight, overweight or obese and examined for metabolic disorders. Metabolic outcomes included:

  • elevated blood pressure
  • fasting glucose levels
  • C-reactive protein
  • insulin resistance
  • hypertriglyceridemia
  • reduced high density lipoprotein cholesterol levels

49% of overweight and 68 % of obese were metabolically abnormal, having more that 2 metabolic outcomes. There was no gender difference. Regardless of weight, independent factors for reduced cardiovascular risk included waist circumference, age and physical activity.

When waist circumference and metabolic syndrome combine, then there may be a connection to liver fibrosis in children. Manco and colleagues studied 197 consecutive Caucasian children aged 3 – 19 years, (136 males and 61 females) with nonalcoholic fatty liver disease (NAFLD) which is a feature of metabolic syndrome. The children were assessed for

  • age and gender
  • body mass index (BMI)
  • components of metabolic syndrome that included waist circumference, high-density lipoprotein cholesterol, triglycerides, blood pressure and glucose

Findings included:

  • 92% of the children had BMI > or = 85th  percentile for gender and age
  • 27% (54 children) were overweight
  • 65% (128 children) obese
  • 84% of children had a large waist (90th percentile or higher)for gender and age
  • 50% had low high-density lipoprotein cholesterol
  • 13% had hypertriglyceridemia
  • 13% had hypertension
  • 5% had impaired fasting glucose or diabetes
  • 10% of the patients had metabolic syndrome.
  • 67% of the children had fibrosis which tended to be mild

Multivariable analysis showed that a large waist was the single component of metabolic syndrome that was incidental to liver fibrosis. Age was also a connection but the most important finding was the link between abdominal fat, waist circumference and liver fibrosis in children with NAFLD Thus the researchers recommend that “the presence of abdominal obesity is an additional criterion for the selection of children and adolescents who should undergo extensive investigation, including liver biopsy”.

Waist circumference is a surrogate measure of visceral fat accumulation. The previous study showed that it can be a predictor of early and late cadiometabolic complications of childhood obesity. Studies have shown that visceral fat, that is fat that is stored in the abdomen, increases the risk for diabetes and cardiac disease.

Stefan et al studied 314 white adults at high risk for type-2 diabetes. They were divided into four groups and classified as normal weight, overweight, obese with insulin sensitivity and obese with insulin resistance. Measurements of subcutaneous abdominal fat, BMI (Body Mass Index) and total body fat were taken. MRI scans were used to ascertain the amount of liver and muscle fat.

The researchers found no difference between the insulin-sensitive and insulin-resistant obese patients with regard to the amount of abdominal or total body fat or BMI. However, it was the distribution of fat that made the difference with high liver and high muscle fat that were predictors of insulin resistance and atherosclerosis.

The obese insulin-sensitive group had almost identical insulin sensitivity as the normal weight group. This was described as ‘relatively benign obesity’. However it is not financially feasible to do MRI scans of all obese patients in order to determine the degree of insulin sensitivity. The researchers concluded that waist and insulin measurements were a appropriate beginning and patients with a family history of heart disease or diabetes should have MRI scans to determine their insulin sensitivity.

 

References:

  1. Manco M, Bedogni G, Marcellini M, Devito R, Ciampalini P, Sartorelli MR, Comparcola D, Piemonte F, Nobili V. Waist circumference correlates with liver fibrosis in children with non-alcoholic steatohepatitis. Gut. 2008;57(9):1283–7.
  2. Wildman RP, Muntner P, Reynolds K, et al. The obese without cardiometabolic risk factor clustering and the normal weight with cardiometabolic risk factor clustering: prevalence and correlates of 2 phenotypes among the US population: (NHANES 1999–2004). Arch Intern Med. 2008;168:1617–1624.
  3. Stefan N, Kantartzis K, Machann J, et al. Identification and characterization of metabolically benign obesity in humans. Arch Intern Med. 2008;168:1609–1616.