00:03Leptin and ghrelin are two hormones that exert opposing influences in the regulation of appetite
00:08and energy balance.
00:11Leptin is produced mainly by fat cells, and circulating leptin levels increase as body
00:15fat increases, reflecting the amount of stored energy in the body.
00:20Leptin acts on receptors in several brain regions, most notably the hypothalamus, where
00:24it suppresses food intake by inhibiting appetite-stimulating neurons and activating neurons that reduce
00:29feeding behavior.
00:32Ghrelin is produced mainly by the stomach, and is released when energy availability is
00:36low, such as during a period of fasting.
00:39Ghrelin levels typically rise before meals and fall after eating, and thus may play an
00:44important role as a short-term driver of hunger and feeding.
00:48Ghrelin also exerts many of its effects through receptors in the hypothalamus, where it activates
00:52neurons that promote feeding behavior.
00:55Ghrelin may also influence the reward system, which could increase food intake for the sake
00:59of pleasure, independent of energy availability.
01:03In general, leptin inhibits hunger and ghrelin stimulates it, and the balance between the
01:08two forms part of a broader system that helps regulate feeding behavior and body weight.
01:13When we lose weight, for example, ghrelin levels tend to increase and leptin decreases, mechanisms
01:19that are thought to help us maintain a consistent weight over time.
01:23The role of leptin and ghrelin in obesity, however, is still unclear.
01:28Leptin levels in obesity are higher than normal, but the brain is often less responsive
01:32to leptin, a phenomenon called leptin resistance.
01:36Ghrelin levels are typically lower in people with obesity, and do not fall as significantly
01:41after a meal, nor rise as much before a meal.
01:43It's possible these more stable ghrelin levels could result in less restricted eating periods
01:49and contribute to obesity, but more research is needed to confirm this.
01:53Let's say...
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