Activity & Weight Loss: It's not Just Exercise you Need

It is a given that reducing caloric intake while simultaneously increasing ones level of exercise results in significant weight reduction. Research in mice has shown that when the animals are reared in an enriched environment they show improved cerebral (brain) health which is defined as an increased level of neurogenesis, enhanced learning and memory, and resistance to external cerbral insults. Enriched environments for lab mice are defined as those that are larger, have running wheels, mazes, and toys that are changed regularly.

An additional unexpected finding from these types of experiments was that the animals in the enriched environments were leaner than littermates reared in a standard laboratory housing environment even though both groups of mice were fed identical diets and had free access to the food.

In research recently published in the journal Cell Metabolism,
  • http://dx.doi.org/10.1016/j.cmet.2011.06.020
  • investigators looked into the role of the enhanced neurogeneis in enriched environment mice. As a background to the results of the study it is important to appreciate that humans, like rodents, contain two distinct forms of fat. White adipose tissue (WAT) is found both subcutaneously (think "beer belly") and viscerally (surrounding the internal organs). WAT is the primary fat storage organ in the body but fat storage is not its only function. Full discussion of WAT function is beyond the scope of this posting but one can find complete details in the Adipose Tissue page of my website. The other type of fat is called brown adipose tissue (BAT). BAT is so-called because it is highly enriched in mitochondria which are loaded with proteins called cytochromes that confer a reddish-brown color to the mitochondria. Until a few years ago it was thought that BAT was only present in new born babies and disappeared after a few months. The primary role of BAT is the process of "adaptive thermogenesis." Adaptive thermogenesis is the process of increased fatty acid oxidation in response to cold. Unlike fat oxidation in WAT which is used to generate ATP energy, fat oxidation in BAT is uncoupled from ATP production and is instead the energy of electron transport in the mitochondria is released as heat. Recent imaging techniques have shown that BAT tissue remains in adult humans and can be induced in response to cold and sympathetic nervous system activation. BAT-like cells are found residing in WAT of rodents and humans and can be identified as such from the expression of the BAT-specific gene UCP-1 (uncoupling protein-1). When these BAT-like cells were examined in mice living in enriched environments it was found that there was an increase in BAT transformation inside WAT. This transformation was associated with resistance to high-fat diet-induced obesity.The increased BAT induction in these animals was demonstrated to be the result of interactions between the hypothalamus and WAT. The hypothalamus is the major feeding and reward center of the brain and as such expresses numerous neurotransmitters that control reward behaviors and feeding behaviors.

    It appears that what is needed for humans is to find the optimal "enriched environment" that is easily attainable to the widest group of individuals as an additional means to fight the obesity epidemic. Whereas, exercise is indeed the best enrichment humans can engae in to fight fat build-up, many individuals can't find access or time to engage themselves, not to mention that obese individuals already have undue strain on their joints such that even mild exercise can be painful.

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