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The Effects of Obesity on Skeletal Muscle Contractile Function



Skeletal muscle

Given that obesity has profound effects on all organ systems, it is not surprising that excess body fat is also associated with a decrease in muscle function.

The complex biology of the molecular, structural, and functional changes that have been associated with obesity are now extensively discussed in a review article by James Tallin and colleagues, published in the Journal of Experimental Biology.

Without going into the molecular details here, suffice it to say that there is considerable evidence to show and explain why muscular function is impaired in both animal models and humans with excess body fat. (For e.g. at a cellular level, the dominant effects of obesity are disrupted calcium signalling and 5′-adenosine monophosphate-activated protein kinase (AMPK) activity. As a result, there is a shift from slow to fast muscle fibre types. There is also evidence for an impairment in myogenesis resulting from disruption of muscle satellite cell activation. Furthermore, muscle function is affected by insulin resistance and decreased adiponectin levels generally associated with obesity).

Although individuals with obesity will often have a larger muscle mass and may well be stronger than “normal-weight” individuals, when corrected for the amount of extra muscle, it is evident that the muscles are less efficient.

In fact, many of the biochemical and structural changes that occur in obesity are very similar to those found with aging. Not surprisingly, when aging meets obesity, things get even worse.

Although the paper does not discuss the reversibility of these changes with weight loss (or obesity treatment in general), I am aware of other data showing that much of the loss of muscle contractile function associated with obesity can be reversed with weight loss.

A clinical correlate of this is the fact that, following weight loss, individuals often find that it takes far more exercise to burn the same number of calories than before (this is not just because the person is now carrying less weight).

Given the increased recognition that lean body mass is an important determinant of overall health and function, clearly this topic is of continuing interest.

@DrSharma
Edmonton, AB

1 Comment

  1. I think it would be a good idea for them to do a study where they take note of muscle function in overweight people, and then follow them over a certain period of time tracking the muscle function, especially for the ones who lose weight. It’d be important to note how they lost weight, what kind of exercise and/or diet they did.

    Also as someone with a connective tissue disorder and weight problems, I am curious as to how many people also struggling with their weight might have a connective tissue disorder and that could be more the cause of muscle function as well as much of the weight gain. My mom has always been very slim, never overweight in her life, and has poor muscle tone and a connective tissue disorder. No matter how much she exercises or stresses over her diet to try to get better, she remains in a weakened state. What’s interesting in my case is that I believe my dad and grandma on his side also carry a connective tissue disorder gene and they are much bigger in height and weight then my mom’s side of the family. I think on my dad’s side, it’s a different genetic code and CTD type than on my mom’s side.

    Dercum’s disease, which I likely have as well as the other connective tissue disorder, tends to contribute to weight gain, though not always. Dr. Herbst believes this is yet another connective tissue disorder.

    Thoughts?

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