Cancer: excess weight leads to increased risk
Perhaps even more disturbing is the current trends linking obesity to 20 different types of cancer. Leading experts in public heath are even predicting that obesity will soon replace smoking as the primary cause of cancer in the developed world. Harvard School of Public Health has estimated that 15% – 20% of cancer cases are associated with obesity, a high number considering tobacco is responsible for 30% of cancer cases.
A study by the British Medical Association published in Lancet in Feb. 2008 reviewed 280,000 cases from 141 studies following both subjects of normal weight and overweight over a nine- to 15-year period. For men who had over 33 pounds of excess fat, there were increased risks of esophageal cancer by 52%, thyroid cancer by 33%, and both colon and kidney cancers by 24%. Women had similar results from 29 pounds of excess fat linked to risks of 51% for esophageal, 34% for kidney, and 60% for both uterine and gall bladder cancers.
The mechanism as to how being obese results in these types of cancer is still unclear. However, all of the evidence seems to point to the systemic effects of the homronal imbalance from the enlarged adipocytes.
Type 2 diabetes
There are approximately 18 million type 2 diabetics in the US, of whom 80% are obese. These 15 million obese type 2 diabetics represent roughly 20% of the 76 million obese in this country. A 2008 review published in the Journal of the American College of Nutrition performed a meta-analysis of clinical studies that suggested 60%-90% of type 2 diabetes cases are related to obestiy or weight gain. There is a strong correlation between obesity and diabetes though no clear culprit linking the two diseases has been identified.
At the cellular level, adipocytes experiencing hypertrophy (growth) are known to release increased levels of the hormone resistin. Many researchers have found a strong correlation (tumor necrosis factor)-alpha increases. TNF-alpha negatively impacts blood sugar absorption by the liver and muscle and signifies another potential cause of insulin resistance.
There is also compelling data showing that a 10% reduction in initial body weight in obese patients dramatically improves glycemic control along with reducing cardiovascular-related risks. Furthermore, obese patients who undergo bariatric surgery and experience substantial excess weight loss are known to experience remission of their type 2 diabetes. This has been achieved with gastric banding, gastric bypass, and vertical banded gastroplasty.