Why Are Some People Obese? - Trends in Obesity Research

Endocrine researchers are actively investigating the root causes of obesity. Recent trends currently being studied aim to identify why obesity affects some people, but not others. The trends of why obesity affects some people include:

Investigating obesity as an energy imbalance: Over an extended period of time, some people may ingest more carbon- and nitrogen-containing compounds from the food they eat than they need for energy (ideally, energy in = energy out), causing them to gain weight. This finding has led to ongoing research to determine how energy imbalance relates to such important overweight and obesity issues such as how food intake is regulated, where fat is stored and how genes control these processes.

Exploring the epidemiological model of obesity: An epidemiological model is a model that includes an environmental agent that acts on a host to produce a disease. In the case of obesity, the environmental agent is food and the host is the obese individual. In affluent societies, such as those of the Western world, foods, particularly foods high in fat, are abundant and physical activity has gradually been reduced. For the individual who may also be genetically susceptible to developing obesity, this excess of food energy leads to an accumulation of fat in cells, and, eventually to obesity. Some endocrine researchers believe that an epidemiological model may be a more comprehensive way to look at obesity than the energy balance model to conceptualize obesity as a disease.

Identifying the impact of select environmental agents on obesity: Environmental agents that have been shown to impact an individual’s risk for gaining and maintaining weight, resulting in overweight or obesity issues include:

• Intrauterine factors such as maternal diabetes, maternal smoking and intra-uterine nutrition⁹³;
• Neonatal environmental factors, such as breast-feeding; infants breast fed for more than 3 months may have a reduced risk of future obesity⁹⁴;
• Adiposity rebound, or the age in childhood when body mass index (BMI) stops falling and begins to rise. Early adiposity rebound predicts future obesity⁹⁵;
• Medications; drug-induced weight gain has been linked to many medications that are designed to treat various diseases such as psychosis, depression, allergies and diabetes⁹⁶;
• Portion size⁹⁷, fat intake⁹⁸ and high fructose corn syrup⁹⁹; all have been implicated as contributors to obesity¹⁰⁰. Research has found a correlation between the consumption of soft drinks and future weight gain in children (see childhood (pediatric) obesity) and adults^{101, 102};
• Activity; low levels of physical activity have been shown to correlate with weight gain and the issue of obesity;
• Smoking; smokers tend to have a lower body weight, and cessation of smoking is generally associated with weight gain¹⁰³ (Note: Smoking is discouraged. Research addresses why the weight
  correlation exists and how to aid patients in quitting without weight gain.); and
• Viruses and obesity; one laboratory has reported that obese humans have higher antibody levels to one strain of adenovirus (AD-36), a viral infection possibly linked to obesity.
  

Researching host agents and obesity: Host agents, or characteristics, have been found through research to impact an individual’s risk for gaining and maintaining weight, and therefore may affect overweight and obesity issues. They include genetic causes and physiological factors.

What Is the Nature of Obesity?
Endocrinologists are currently researching the pathologic basis for obesity by studying the size and volume of fat cells, in searching for keys to the obesity issue. Once the true nature of obesity is revealed, endocrinologists will be armed with greater knowledge of how to manage and treat obesity in the clinical setting¹⁰⁴.