The Effect of Combined Exercise and Diet on Obese Mice
Obesity is a metabolic condition resulting from an imbalance between the energy consumed and the energy expended. This is often caused by an increase in the intake of calorie-dense foods and a decrease in physical activity, leading to an abnormal build-up of fat. Such fat accumulation can have serious health consequences, raising the risk of chronic diseases like cardiovascular conditions, diabetes, and some cancers. It is usually associated with a higher prevalence of non-alcoholic fatty liver disease (NAFLD) and asthma.
While combining exercise and diet is majorly used as conservative measures in the treatment of obesity, a study by Marain NF et al.1 highlighted the impact of intensive exercise and diet on the respiratory system and obesity-related parameters in mice.
Mouse Model and Method
From 8 weeks of age, thirty-two C57BL/6 mice were fed a high-fat diet (HFD) containing 60% fat. At 27 weeks, they were divided into four groups:
- HFD + no exercise (HFD/NE)
- HFD + exercise (HFD/E)
- NCD + no exercise (NCD/NE)
- NCD + exercise (NCD/E)
The exercise protocol was designed to induce bronchoconstriction in predisposed mice without causing airway hyperreactivity or inflammation in controls.
Lung Function Assessment
Forced oscillation technique (FOT) maneuvers and forced expiratory measurements were performed using the flexiVent system provided by SCIREQ. A small-particle-size Aeroneb Lab nebulizer (2.5–4 µm) was integrated for methacholine administration.
Following a precise sequence of maneuver, measurement of airway hyperresponsiveness (AHR) and forced expiratory parameters in response to increase concentration of methacholine was performed.
The outcomes of these measures across the different groups were as follow:
- Higher baseline IC (Inspiratory Capacity) in HFD/E compared to HFD/NE group
- Lower tissue elastance in NCD/NE compared to HFD/NE group
- None of the groups showed signs of airway obstruction
- small airway resistance was significantly lower in NCD/NE compared to HFD/NE group
Additional Tests
The lung function assessment was followed by a series of tests and measurements on blood, lung cells and liver, including steatosis, fibrosis, and inflammation scoring. The body weight evolution was assessed all along the protocol.
Conclusion
This study confirmed that exercise alone is not sufficient to induce significant weight loss, and that the combination of exercise and diet is the most efficient for weight reduction, also helping to reduce the percentage of steatosis in the liver of mice and small airway resistance.
However, it also induces modest but significant airway hyperreactivity and pulmonary inflammation, highlighting the importance of exercise intensity control.
References
1 Marain, N.F.; Jonckheere, A.-C.; Dilissen, E.; Cremer, J.; Roskams, T.; Colemont, M.; Bullens, D.M.; Dupont, L.J.; Vanoirbeek, J.A. Combined Exercise and Diet Induce Airway Hyperreactivity While Reducing Liver Steatosis in Mice with Diet-Induced Obesity. Nutrients 2024
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