What causes us to feel hungry? Introducing a little hormone called ‘Leptin’

By Jayne Robinson

move your frame leptin

Ever wondered why some people just need to eat more than others? It's not self-discipline, it's actually about hunger and a hormone called leptin. Chris Sandel explains.

Chris Sandel is a nutritionist and runs the company 7 Health. He specialises in helping clients ending dieting, reproductive issues and disordered eating. For the Frame blog he helps to shed some light on the reasons why some people feel hungrier and therefore eat more than others… it’s all about the leptin.

For “normal eaters” (those who don’t diet or participate in emotional or disordered eating practices) maintaining a stable weight requires little conscious effort. Sure, they may not have the “body of their dreams” or they may be sitting at a weight that is higher than they would “like,” but despite this, their weight is relatively stable.

And this isn’t because they eat the same exact amount every day. Some days they eat more and some days they eat less. Some days they feel ravenously hungry, other days they barely think about food.

As part of our physiology we have a feedback system that controls our weight and our hunger. And central to this feedback system is a hormone called leptin.

Leptin was discovered fairly recently in 1994. It is produced and released from fat cells, acting on the brain, to reduce food intake and increase energy expenditure.

When you get hungry it is because leptin levels have fallen. Then as you eat a meal, leptin levels increase, signaling to your body that you are no longer hungry and that you don’t need to eat anymore.

Leptin is secreted by fat cells and its blood levels are proportional to body fatness. The more fat someone has, the more leptin they release. So in theory as fat mass increases, hunger should be reduced, as the body tries to burn more calories to reduce fat back to its normal levels.

But if this is the case, how can someone become obese and start carrying significantly higher amounts of body fat?

When leptin was first discovered, it finally felt like they had discovered this magic weight loss pill. The theory was that in people who are carrying extra weight, something must be broken with their leptin production.

So they decided to do a trial with overweight and obese people and give them extra leptin. Unfortunately for nearly everyone in the trial it did nothing. This didn’t make sense.

They decided to take everyone off the leptin and look at it again. What they found was that the participants’ normal levels of leptin were already unusually high. So if leptin was high then why were they still hungry and not losing weight?

The way hormones work is that they are released into the blood and travel to a receptor site somewhere in the body. Once it gets to the receptor site it creates some kind of change or action in the body.

The problem wasn’t with the amount of leptin but with its signalling ability, a condition now referred to as leptin resistance. Despite releasing the leptin, the body doesn’t get the message properly; so more leptin is released (basically the leptin now shouting it’s message) in an attempt for it to get through.

We are still in the early days with research around leptin and leptin resistance but it demonstrates that issues around obesity aren’t about lack of willpower but rather to do with brain function. This isn’t to say that habits aren’t important, as they are. But the idea that we as a society have collectively lost our willpower over the last hundred years, which is so often portrayed, is clearly nonsense.

What is still up for debate, and will be for a while, is what causes leptin resistance. One of the most likely answers to this question is highly palatable food. The kind of food not found in nature, but played around with in a laboratory to get the tastes and flavours just right to give us the biggest reward hit in the brain.

As more of these foods have infiltrated our everyday eating, the more we have seen the symptoms in society at large of leptin resistance.

I’m always one to recommend a fairly relaxed attitude around food. Too many of the clients I see have become neurotic with their eating to such a point it is significantly damaging their health. But despite this, for most people, the majority of the foods they eat should be based around whole foods – fruits, vegetables, meat, fish, dairy, eggs, beans, pulses -this kind of thing.

It is not just that this food is good for our physical body, but rather because it actually effects the signals in our brain. And this is something way stronger than willpower.

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