The FastDay Forum

[carorees]

Oh, yes, you're right, I'd forgotten. But I do remember there was something about the sensitivity of the stretch receptors in the stomach being affected by the emptiness during a fast, so that although the size is not affected, it feels like it has been. Now where did I read that? I think I did post a link last time we discussed it.

Ghrelin secretion when the stomach is full from memory - popped up somewhere on TV when they had some soldiers eat a meal either as is or liquidised and the latter kept them "full" for longer.

The magnitude of a nocturnal rise in leptin concentration is proportional to the nutritional state at the onset of darkness. Nocturnal leptin concentration and presumably its lipolytic action[33] are greater in response to energy surplus and lower after energy depletion.[31] Dawn and dusk nadirs of human hunger (Fig. 6) may reflect circadian transition from higher nocturnal leptin concentrations when lipolysis is increased and behavioral activation blocked to the lower diurnal leptin concentrations when leptin may affect the motivation to locomote in conjunction with meal eating. When humans deliberately truncate the period of nocturnal rest, declines in plasma leptin and increases in plasma ghrelin are associated with increased appetite and presumably greater fat synthesis.[29] However, as levels of obesity rise and tissue resistance to leptin action increases,[26] nocturnal lipolytic effects of leptin would be expected to decline and tend to maintain higher body fat levels.

This gives a possible explanation for why obesity is linked with poor sleep. And it might also indicate that saving all ones calories for the evening meal on a fast day might result in more nocturnal lipolysis and so be slightly more effective than spreading ones calories?

Could you explain the latter point? I don't quite see it. It seems to me that the benefit of saving the fast day calories until dinner is that it results in a 24 hour period during which there is no food intake to interrupt lipolysis, but maybe that's too simplistic?

[carorees]

Yes, the lipolysis during the 24 hour fast is a benefit too, but my comment was with respect to the nocturnal rise in leptin. So, going to bed having eaten a reasonable sized meal (500-600 cal) would hopefully result in a bigger leptin rise and hence more lipolysis at night as well as during the day?

You could go further and speculate that eating your evening meal during daylight hours might also be beneficial, but as artificial lighting tends to interfere with our natural circadian rhythm perhaps just not eating in low light levels would do? (Shame! This implies we have to cancel those romantic candlelit dinners!).

Ah okay, I see your point now. Of course, if there's leptin resistance, as there probably is, that would interfere with the effect. BUT fasting seems to hit the "reset button" on many of these feedback systems, so I'd expect it to have a similar effect on leptin sensitivity.