RE: Re: exercise and food restriction

[Guest guest]

>>But the earlier study, which I had noted, said rapid weight loss (a

greater caloric deficit) uses more lean body mass for its source of

calories, than slow weight loss.

>>But the study you referenced says that fasting, i.e. very rapid

weight loss, uses mostly fat to make up the deficit. So do we really

have a 'U' shaped fat function here? Such that a small caloric

deficit and a very large caloric deficit burn fat, but a moderate

caloric deficit tends to burn mostly LBM?

Part of the reason, may be due to the " fasting " state. After around 48 (24-36)

hours, or so, of fasting the body switches its metabolism from a " fed " state

into a " fasting " state. When carbohydrates are almost or completely depleted,

the body starts conserving its protein stores (ie, muscles). It starts burning

ketones as a preservative measure against losing any excess lean body mass. The

brain and nervous system were using some protein to fuel it thru a process

called " gluconeogenesis " , where protein is converted to glucose to fuel the

brain. The body than starts producing ketones from fat tissue, which the brain

can use as a secondary fuel source. Hence consrving lean body mass.

This is what enables most animals to fast for lengths of time, without losing

excess lean body mass and keep their brains fueled.

Regards

Jeff