As reported in the January 2 edition of the Journal of Clinical Investigation, subjects were encouraged to eat 1,000 extra calories per day, mainly by going to fast food restaurants with the objective of adding six percent of their body weight. According to the study's chief author and assistant professor of medicine Elisa Fabbrini, "This was not easy to do. It is just as difficult to get people to gain weight as it is to get them to lose weight."'
The 20 obese participants in the study were asked to gain about 15 pounds over several months to determine how the extra pounds affected their metabolic functions. Research participants were asked to eat 1,000 extra calories every day until gaining 6 percent of their body weight.
People who were not suffering from ailments typically associated with obesity -- such as insulin resistance, high cholesterol, high blood pressure and excess liver fat -- at the beginning of the study did not have these problems even after gaining about 15 pounds to their already overweight frames, according to the findings. The results echo what scientists have witnessed in the general population, which is that about one-fourth of obese people do not appear to suffer from metabolic issues that can lead to heart attack, diabetes and stroke. On the other hand, people who did suffer from metabolic problems before the study got even worse when they gained additional weight.
After the study, all of the research subjects were helped by dieticians to lose the weight they gained. The study was featured on HBO's documentary, Weight of the Nation, during the time the research was conducted.
As a result of the study, the researchers think they now understand better how to distinguish obese people who will be more prone to ill health from those who may be more protected. For example, people with abnormal metabolisms accumulated fat in their livers, while the healthier people did not, even when they gained more weight.
Another difference was gene function in fat tissue, according to the study results. The researchers determined that overweight people with normal metabolisms had more fat-regulating genes. While the activity of those genes increased even more when the metabolically normal people gained weight, that was not the case for people with abnormal metabolism, the report said.
Because obesity can contribute to dozens of health problems, the scientists believe that more research is needed to figure out why some are particularly prone to problems from obesity. Senior investigator Samuel Klein, director of Washington University's Center for Human Nutrition, said, "Could it be genetics, specific dietary intake, physical lifestyle, emotional health or even the microbes that live in the gut? We need more studies to try to understand why obesity causes specific diseases in some people but not in others."
He added, "This research demonstrates that some obese people are protected from the adverse metabolic effects of moderate weight gain, whereas others are predisposed to develop these problems. This observation is important clinically because about 25 percent of obese people do not have metabolic complications. Our data show that these people remain metabolically normal even after they gain additional weight."
As part of the study, the researchers helped the subjects lose the weight they had gained. They lost all of the weight they had gained, or more.