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.