Little diet pain, big health gain

"These results demonstrate you get a large bang for your buck with a 5% weight loss," says senior study author Samuel Klein of Washington University School of Medicine. "Based on these findings, we should reconsider changing current obesity practice guidelines to stress a target goal of 5% weight loss, rather than 5% to 10% weight loss, which increases the perception of failure when patients do not achieve weight losses that are greater than 5%."

Obesity is a major risk factor for a number of chronic diseases, including diabetes, cardiovascular disease, and cancer. Most treatment guidelines, including those recently proposed by several major medical and scientific societies, recommend moderate weight loss of 5% to 10% to achieve improvements in metabolic function and health. "However, it is much easier to achieve a 5% weight loss than it is to achieve a 10% weight loss, so it is important to understand the health benefits that occur with a 5% weight loss and what additional benefits can be expected with more weight loss in people with obesity," Klein says.

To date, several large randomized controlled weight loss trials have evaluated the effects of different amounts of weight loss on clinical outcomes. But until now, none have separated the weight loss outcomes in those who achieved 5% weight loss from those who achieved 10% weight loss. Klein and his team set out to address this question by randomly assigning 40 obese individuals to either maintain their body weight or go on a low-calorie diet to lose 5%, 10%, or 15% of their body weight.

Importantly, all of the study participants showed signs of insulin-resistant glucose metabolism--a major risk factor for type 2 diabetes. When blood glucose levels rise after a meal, beta cells in the pancreas release a hormone called insulin into the blood, stimulating muscle, fat, and liver cells to take up the excess glucose. But in individuals with insulin resistance, glucose builds up in the blood instead of being absorbed by the cells, increasing the risk of type 2 diabetes.

Among the 19 individuals who lost 5% of their body weight, beta cell function improved significantly, as did insulin sensitivity in fat tissue, liver, and skeletal muscle. Meanwhile, the nine participants who achieved additional weight loss showed further improvements in beta cell function and insulin sensitivity in muscle tissue. "Taken together, the findings show that 5% weight loss is sufficient to improve health outcomes, with additional weight loss further decreasing risk factors for metabolic and cardiovascular diseases," Klein says.

According to the authors, future studies should evaluate the effect of progressive weight loss on other obesity-related complications, such as arthritis and lung disease. It will also be important to test whether the findings apply to people with diabetes and to examine the cellular basis for the observed therapeutic effects.

In the meantime, Klein hopes that this study will serve as a motivating force to help people achieve manageable weight loss goals. "Our findings show that even a small amount of weight loss has important health benefits for multiple organ systems," he says. "We hope that these findings will encourage obese people to take reasonable steps to watch what they eat and increase their physical activity, because this will translate into a lower risk for diabetes and heart disease."