Twenty-five years ago, the only known appetite-controlling hormone was insulin.
When blood insulin levels are high, glucose gets stored as glycogen and fats get stored in adipose tissue. The resulting reduction in circulating fuels, such as glucose and free fatty acids, then stimulates appetite.
This leads to the common experience of being hungry 2-3 hours after a high carbohydrate, low fat meal.
Leptin and Ghrelin
But in the interim, we have discovered many other circulating and cellular signals that communicate the body’s energy status and regulate energy intake (aka appetite) as well as metabolism.
Among these regulatory hormones are leptin (made primarily in adipose tissue), and ghrelin (made in the upper digestive tract).
Both have specific receptors in the brain that transmit their biochemical message into behaviors – for leptin it is “eat less” and for ghrelin it is “eat more”.
Individuals on a low carbohydrate diet who experience weight loss exhibit a significantly greater reduction in leptin levels compared to those on a low-fat diet.
That would normally be a signal to eat more, but here’s a key fact — the brain’s sensitivity to the leptin signal goes way up when on a well-formulated ketogenic diet.
Leptin Resistance and Inflammation
Another key fact – the brain’s response to leptin is inhibited by inflammation, resulting in leptin resistance.
Since we now know that inflammation is dramatically reduced by sustained nutritional ketosis, it appears that the reduction in leptin resistance due to reduced inflammation more than compensates for the lower leptin levels.
In other words, on a well-formulated ketogenic diet the brain perceives a greater satiety response to less leptin.
This reduction in inflammation and increase in sensitivity to leptin, together with the reduced blood insulin levels characteristic of nutritional ketosis can explain the paradox as to why we see a decrease in appetite with nutritional ketosis.
Leptin and sleep
As far as leptin goes, it appears that the typical modern lifestyle (fast food, little or no exercise, too much stress and not enough sleep) greatly contributes to its disruption, with lack of sleep being a major culprit. (Source: Diabetes UK)
The composition of the meal that breaks the fast seems to matter to keep ghrelin levels in balance. Ghrelin is least affected by fats, whilst carbs often cause a rebound hypersecretion in ghrelin.
Increasing protein especially is one way to limit hunger and may even maintain satiety in the face of high ghrelin. Ghrelin is also higher when sodium intake is low, so maintaining a good salt intake could make a difference. (Source: Diabetes UK)