As a trained physicist I am more interested in the "why's" than in the "what's". It is old hat that the
combination of diet (usually incorporating a moderate caloric reduction) and exercise still is the most promising way to sustainable weight loss and metabolic health. The molecular and genetic underpinnings of their almost magical synergy, however, have still not been 100% elucidated. A recent study (
Fu. 2011) from the
Tianjin Medical University in Tianjin, China, does now contribute another piece to the complex puzzle that is our metabolism.
Published in the latest issue of the clinical and experimental branch of
Metabolism Li Fu and his colleagues report the results of an experiment in the course of which 40 mice were assigned to one out of four intervention groups, two of which exercised on a mouse-treadmill for 60min/d five times per week in the course of the 6 week experiment:
- normal chow + treadmill exercise (NE)
- high fat diet + treadmill exercise (HE)
- normal chow + sedentary (NC)
- high fat diet + sedentary (HC)
The effect of the individual treatments at the transcriptional level, and selected genes were evaluated via oligonucleotide microarray measurements and confirmed by real-time polymerase chain reaction. As could be expected, the data showed "that
6 weeks of aerobic exercise improved the plasma lipid profile and reversed the glucose intolerance" in the high-fat fed mice.
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Figure 1: Changes in body weight and blood parameters vs. sedentary control on normal diet
(calculated based on data from Fu. 2011) |
Of greater importance, however, are the
503 genes of which the scientists found that they were "
differentially expressed in samples of HCmice as compared with those of the NC group". By inter-group comparisons, Fu et al. were able to assign 40 of these genes to the effects of aerobic exercise.
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| Figure 2: Univariate variance analysis on body weight and plasma parameters (data adapted from Fu. 2011) |
As the data (significance values) from a univariate variance analysis in figure 2 goes to show, the high fat diet (HFD) was associated with significant negative (red) effects on body weight, free fatty acids (FFA) and high density lipoprotein (HDL).
Aerobic exercise, on the other hand, had beneficial effects on insulin total cholesterol and triglycerides, it did not, however, as so many frantic dieters expect, significantly reduce body weight. Neither did it prevent the HFD induced weight gain and that despite profound effects on the other negative effects of high fat feeding measured in this study.
These results stand in line with observations of Gary O'Donovan and colleagues (
O'Donovan. 2011), published in the same journal. In a cohort of
183 nonsmoking white men aged 35 to 53 year O'Donovan and other researchers from the United Kingdom found
profound differences in traditional and novel cardiometabolic risk factors (high-density lipoprotein cholesterol, triglycerides, alanine aminotransferase, and insulin resistance)
between subjects who were fat and fit (like the exercised HFD mice)
and those who were fat and unfit (like the unexercised HFD mice).
Taken together, these two studies confirm what many of you probably already knew:
Aerobic exercise can ameliorate, yet not reverse, the damage you are inflicting upon your self by bad dietary habits (these are not the same for mice and men! A high fat diet - done properly - does not have to be detrimental to human health). Most importantly, aerobic exercise alone (and compensatory overeating) won't make you lose fat -
in combination with appropriate lifestyle changes (note: I do not use the word "diet"!)
and muscle building resistance training, it will do both: help you lean out and live a longer and healthier (an probably happier!) life.
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