Hormones and Metabolism: what the experts say

The Big Picture

In these conversations, metabolism is run by hormones rather than by willpower or arithmetic alone. On Huberman Lab, Andrew Huberman's takeaway is that thyroid hormone and growth hormone are the master dials of metabolism, deciding how the body uses nutrients, draws on fat, repairs muscle, bone and cartilage, and supports the brain [2]. He stresses that the brain is the dominant consumer: if you lay in bed and did nothing but think, that would account for about 75% of your metabolic needs [1]. That is why, he says, these hormones matter not only for body composition but also for cognitive function across the lifespan [1].

The other two sources turn to food and fat. Huberman explains the hormones that drive hunger and fullness, from ghrelin and CCK to insulin [3]. On The School of Greatness, Shawn Stevenson describes fat as an organ in its own right that communicates across the body and produces its own hormones, and says, "Our fat is programmed to do what we've taught it to do" [4].

Where the Experts Agree

Insulin and glucagon are a pair. Stevenson calls them brothers directed by the pancreas: insulin's job is to store energy, and glucagon does the opposite, telling cells to release energy, but it cannot work while insulin is active [4]. Huberman says that when you're hungry, glucagon pulls stored energy from the liver and muscles and eventually from body fat [3].
Insulin is essential, not an enemy. Stevenson says it is essential for survival, as type 1 diabetes shows [4]. Huberman notes that type 1 diabetics lack insulin, while type 2 diabetics produce it but are insulin insensitive, usually in association with excess weight [3].
Calories are not the whole story. Stevenson's conversation explains why calories are not the whole story [4]. Huberman describes an inpatient study in which adults ate ultra-processed or unprocessed diets for 14 days, matched for calories, sugar, fat, fiber and macronutrients; those on the processed diet ate much more and gained weight beyond what extra calories alone could explain [3]. His conclusion is that "a calorie is not a calorie" when it comes to highly processed food [3].
Sleep is part of metabolism. For growth hormone, Huberman recommends protecting deep early-night sleep [2]. Stevenson says about 84 percent of fat leaving the body is eliminated through the lungs as carbon dioxide, and that about a third of that happens during sleep [4].
Hormone systems follow a logic you can learn. Huberman lays out a repeating pattern: neurons in the hypothalamus release so-called releasing hormones, these signal the pituitary, and the pituitary releases stimulating hormones that act on a target gland [1]. Stevenson uses a movie theater analogy, with two enzymes as ushers: lipoprotein lipase ushers triglycerides into the fat cell, and hormone-sensitive lipase ushers them out [4].

Where They Differ

The sources largely agree; they differ in which lever they pull and how far they push it.

Which hormones get the attention. Huberman's metabolism episode centers on thyroid and growth hormone and the brain-to-pituitary-to-tissue logic they share [2]. Stevenson centers on fat itself and on insulin and glucagon [4].
Adherence versus food quality. Huberman cites Stanford colleague Christopher Gardner's research finding that different diets produced equivalent weight loss when people stuck to them, making adherence the key factor [3]. Yet he also sees highly processed foods as a major driver of the rise in diabetes and obesity worldwide [3].
More metabolism versus healthy metabolism. Huberman points out that muscle and related tissues burn more energy than fat, so metabolism can be raised by adding muscle and reducing fat [1]. But his larger theme is that a healthy, not excessive, metabolism supports lean tissue, bone, injury repair and clear thinking [1].
Habits versus injections. Huberman says straightforward behaviors may even offset the steep decline in growth hormone that begins in our 30s, while injected hormones and peptides come with risks worth understanding before anyone considers them [2].
What fat loss means. Stevenson says fat cells are storage containers; you do not kill them, you get them to release their contents to be used as fuel [4]. Huberman frames body composition in terms of adding muscle and reducing fat [1].

Practical Takeaways

For thyroid, Huberman points to getting enough iodine, L-tyrosine and especially selenium, for example from Brazil nuts or animal foods [2].
For growth hormone, protect deep early-night sleep and don't eat within two hours of bed [2].
Exercise for up to about an hour with a real warm-up and a prompt cool-down, as Huberman describes [2].
Arginine or carefully managed sauna sessions are possible additions he mentions for growth hormone [2].
Pick a diet you can stick to: in the Gardner research Huberman cites, adherence was the key factor [3].
Cut back on highly processed food, which led people in the inpatient study to eat much more [3].
Keep blood glucose in the healthy range Huberman gives, roughly 70 to 100; chronically high glucose damages neurons [3].
Think of fat loss as release, not destruction: Stevenson says glucagon cannot tell cells to release energy while insulin is active [4].