In New Zealand 1 in 5 adults are obese and overweight. Obesity is a risk factor for many chronic diseases including type 2 diabetes, heart disease, hypertension and stroke, gallstones and some cancers. Nutrition-related factors including obesity are major risk factors for causes of death in New Zealand. The effect of increased body mass index (BMI) was estimated to be responsible for 11.5 percent of all deaths in 1997. Evidence is emerging to suggest that the prevalence of overweight and obesity is increasing worldwide at an alarming rate. New Zealand is no exception. The World Health Organization has estimated that the cost for obesity is 2 to 7 percent of the annual health budget, which equates to $303 million in New Zealand.
Obesity is a condition in which the natural energy reserve, stored in the fatty tissue of humans and mammals, is increased to a point where it is a risk factor for certain health conditions or increased mortality. Obesity develops from the interaction of individual biology and the environment. Excessive body weight has been shown to correlate with various diseases, particularly cardiovascular disease, diabetes mellitus type 2, sleep apnea, and osteoarthritis. When food energy intake exceeds energy expenditure, fat cells (and to a lesser extent muscle and liver cells) throughout the body take in the energy and store it as fat. In its simplest conception, therefore, obesity is only made possible when the lifetime energy intake exceeds lifetime energy expenditure by more than it does for individuals of "normal weight".
Factors that have been suggested to contribute to the development of obesity include:
- Genetic factors and some genetic disorders (e.g., Prader-Willi syndrome)
- Underlying illness (e.g. hypothyroidism)
- Certain medications (e.g., atypical antipsychotics)
- Sedentary lifestyle
- A high glycemic diet (i.e., a diet that consists of meals that give high postprandial blood sugar)
- Weight cycling, caused by repeated attempts to lose weight by dieting
- Eating disorders (such as binge eating disorder)
- Stressful mentality
- Insufficient sleep
- Smoking cessation
The mainstay of treatment for obesity is an energy-limited diet and increased exercise. In studies, diet and exercise programs have consistently produced an average weight loss of approximately 8% of total body mass on average (excluding study drop-outs). While not all dieters will be satisfied with this outcome, studies have shown that a loss of as little as 5% of body mass can create enormous health benefits.
