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Clinical Trial Summary

Obesity is reaching epidemic proportions and threatens both health and quality of life of people around the world. While many individuals succeed at short term weight loss, weight loss maintenance is the greatest barrier to successful treatment of obesity. High levels of physical activity are consistently associated with success in weight loss maintenance. The major goal of this proposal is to understand how and why high levels of physical activity are critical for long term maintenance of weight loss. This project takes advantage of the National Weight Control Registry (NWCR), which follows over 6000 individuals who have maintained a weight loss of ≥30 pounds for ≥1 year. Understanding how individuals successful at weight loss maintenance achieve energy balance will provide important insight into strategies to help more people sustain a weight loss.

Clinical Trial Description

Participants were recruited in three groups: weight loss maintainers (WLM: maintaining ≥13.6 kg weight loss for ≥1 year), normal weight controls (NC: Body Mass Index (BMI) matched to current BMI of WLM), and controls with overweight/obesity (Overweight Controls (OC): BMI matched to pre-weight loss maximum BMI of WLM). The investigators hypothesize that total daily energy expenditure (TDEE) in WLM is similar to OC but is significantly higher then NC. High levels of volitional physical activity may compensate for the reduction in energy expenditure ("energy gap") that is the expected result of weight loss. This allows WLM to maintain a high level of "energy flux", which may facilitate optimal body weight regulation over time. The investigators will use doubly labeled water to compare TDEE in WLM and both NC and OC. The investigators will also compare individual components of TDEE including resting energy expenditure (REE), thermic effect of food (TEF), physical activity energy expenditure (PAEE), and physical activity level (PAL) between groups. The investigators also hypothesize that REE in WLM is similar to controls of both types under free living conditions, but will decrease following a period of physical inactivity and be significantly less than controls. Studies in rodents have consistently shown evidence of an increase in metabolic efficiency in the reduced obese state manifested by a lower than predicted REE. Studies in humans have shown mixed results, however few studies have controlled for habitual level of physical activity. Recent evidence suggests REE is greater in adults who perform regular exercise than their sedentary peers; this difference can be attributed in part to greater tonic sympathetic nervous system stimulation of REE that occurs in habitually exercising adults. The investigators believe there is an increase in metabolic efficiency in the reduced obese state manifested by a lower than predicted REE, and that high levels of physical activity function to "mask" or "correct" this metabolic efficiency. The investigators will compare REE under free living conditions and during an experimentally imposed period of reduced energy flux (restricted physical activity matched by an equivalent reduction in energy intake) in WLM and controls. ;

Study Design

Related Conditions & MeSH terms

NCT number NCT03422380
Study type Observational
Source University of Colorado, Denver
Status Completed
Phase N/A
Start date October 2009
Completion date September 2012

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