Researchers Building a Better Weight-Loss Simulator

by U.S. Medicine

November 10, 2011

A model created by NIH researchers challenges some commonly held diet beliefs, including that eating 3,500 fewer calories, or burning them through exercise, always results in a pound of weight loss. The mathematical model takes into consideration patient weight, diet and exercise habits to simulate potential outcomes. The findings were published in the Aug. 26 issue of Lancet. 1

The computer simulation indicates the assumption that a 3,500-calorie deficit resulting consistently in a lost pound is an overestimation of weight loss, because it does not take into account changes in a person’s metabolism — changes that can differ significantly from person to person.

However, the model was designed as a research tool, not as a weight-loss guide to the general public. The simulation allows researchers to put hypothetical patients through diet-and-exercise regimens that never could be done in real life as a way to help design personalized weight-management programs for actual patients.

To test the model, researchers compared predicted weight changes found during simulations against actual changes in real patients. The designers are developing research tools to simulate physiological differences between people, such as gender, age, height and weight, as well as body fat and resting metabolic rate.

The researchers discovered the importance of taking body fat content and body type into consideration when they found that people’s bodies adapt differently to changes in dietary intake. Heavier people get greater weight change with the same change in diet but take a longer time to reach a stable body weight compared with people who have less fat.

More complex mathematical simulations such as this one will help impress on patients how long it takes to make a long-lasting change in body weight, explained Kevin Hall, PhD, an obesity researcher at the National Institute of Diabetes and Digestive and Kidney Diseases and author of the paper. “By using our model to track progress, clinicians can help people reevaluate their goals and ability to achieve them at the pace they want.”

The tool is available for use at http://bwsimulator.niddk.nih.gov.

1: Hall KD, Sacks G, Chandramohan D, Chow CC, Wang YC, Gortmaker SL, Swinburn BA. Quantification of the effect of energy imbalance on bodyweight. Lancet. 2011 Aug 27;378(9793):826-37. PubMed PMID: 21872751.

Obesity and PTSD Linked in Gulf War Veterans

Gulf War-era veterans who are obese are more likely to have chronic health conditions, including PTSD, according to a recent study by VA’s Office of Public Health hand Environmental Hazards. 1

Researchers looked at overweight, obese and non-obese veterans of the 1991 Gulf War, using results from a survey conducted in 2003-2005 among 15,000 Gulf War veterans. Nearly half of Gulf War-era veterans were overweight, and almost 30% were obese.

In multivariate analyses, PTSD was associated positively with obesity after adjusting for age, sex, Gulf deployment status, rank, income, education and current smoking status. Without adjusting for those factors, researchers also saw increases in unexplained multisymptom illness (MSI), chronic-fatigue syndrome (CFS)-like illness and other chronic health conditions among obese and overweight veterans.

Regarding MSI and CFS-like symptoms, the researchers noted there still are large gaps in knowledge about the causes of these conditions, sometimes referred to as Gulf War syndrome. For example, links have been found between environmental exposures and MSI, which were not taken into account in this study.

Also, the researchers noted that these veterans are advancing in age and are at an increased risk for some chronic diseases.

PTSD and depression also have been known to affect diet and activity. A patient suffering from either may be less likely to remain active or to eat a healthy diet, resulting in obesity. Dietary information was not collected as part of the study.

1: Coughlin SS, Kang HK, Mahan CM. Selected Health Conditions Among Overweight, Obese, and Non-Obese Veterans of the 1991 Gulf War: Results from a Survey Conducted in 2003-2005. Open Epidemiol J. 2011;4:140-146. PubMed PMID: 21731594; PubMed Central PMCID: PMC3125597.

Researchers Building a Better Weight-Loss Simulator Cont.

Success of VA MOVE! Program Depends on Support of Management

For more than five years, VA has been encouraging veterans to lose weight and become more physically fit through its MOVE! Weight Management Program. A recently released evaluation of the program shows that its methods are successful, although sometimes facilities must overcome barriers to institute it in some patient populations. 1

Nearly 300,000 veterans have participated in MOVE! since 2006. While the program has found overall success among patients, the success of implementation at medical centers has varied. According to researchers using data collected during the second year of the program’s implementation, a facility’s success in implementation directly correlates with the support the program gets from management, the amount of resources devoted to it and the degree to which it fits with existing programs.

At VA facilities that showed high implementation of the program, managers helped to establish supportive practices and infrastructure by increasing program visibility, dedicating staff time and making it clear to service chiefs that the participation of their staff was expected.

Researchers found that none of the facilities they examined provided phone-based self-management support for patients, which is a foundational treatment component of the program. Staff at the facilities told researchers that they did not feel confident in their ability to help veterans over the phone.

As a result of this finding, VA’s National Center for Health Promotion and Disease Prevention (NCP), which originally developed MOVE!, is piloting a national call center to provide self-management support for veterans.

1: Damschroder LJ, Goodrich DE, Robinson CH, Fletcher CE, Lowery JC. A systematic exploration of differences in contextual factors related to implementing the MOVE! Weight Management Program in VA: A Mixed Methods Study. BMC Health Serv Res. 2011 Sep 30;11(1):248. [Epub ahead of print] PubMed PMID: 21961925.

Compound Improves Health, Survival in Obese Mice

Obese mice lived healthier, longer lives after being treated with a synthetic compound found to improve liver, pancreas and heart function. The National Institute on Aging (NIA)-supported study has implications on the biology of aging and suggests that years of healthy life can be chemically extended, at least in an animal model.

The compound — SRT1720 — a patented molecule, activates the SIRT1 enzyme, which belongs to a class of enzymes called sirtuins that have been linked to the aging process and to dietary restriction. Scientists compared the health of middle-aged mice fed on a high-fat diet that were given a high dose, low dose or no dose of the compound.

While all mice on the diet gained weight, mice treated with a high dose of the compound lived an average 18% longer. These mice also had less fat accumulation on their livers and showed less insulin resistance. Also, mice given the high dose had a higher percentage of high-density lipoprotein, which has been associated with good cardiovascular health.

Researchers noted that it is too early to tell whether these results could be replicated in other animal models, much less in humans, and that further research is necessary before considering SRT1720 as a possible treatment for the diseases of human aging.

1, Minor, RK, Baur, JA, Gomes, AP, et al. SRT1720 improves survival and healthspan of obese mice. Sci. Rep. 2011; 1, 70; DOI:10.1038/srep00070

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