Is leptin the starvation hormone?

Last week in Part 1 of The Hormone Series,  I discussed insulin, a key hormone in weight regulation, controlling fat storage and fat burn. But it does not work alone. It works in tandem with the hormone, leptin. I spoke of the dangers of elevated insulin levels, insulin resistance, and how to improve insulin sensitivity. Today I want to talk about another risk of elevated insulin levels, and that is that it may influence leptin sensitivity.

Is leptin the starvation hormone?

The starvation hormone

Leptin, labelled the starvation hormone by Dr Robert Lustig, is a critical fat cell hormone discovered in the 1990s. It is responsible for signalling to the hypothalamus in the brain that the body has stored enough fat, and therefore has abundant energy to expend. People without leptin, or with their leptin being blocked in some way, act as if they’re in a state of perpetual starvation, with insatiable hunger, no matter how overweight they have become.

How insulin and leptin work together

Here’s a simple way to explain how Insulin and leptin work together. You eat something high in sugar (say a chocolate bar for example). Your blood sugar rises, insulin increases and moves the glucose into the fat cells for storage. Leptin is released from the fat cells and goes to the brain to tell the brain that the body has enough energy on board and to stop eating. In essence it has trigged satiety. The fight or flight response is also triggered here, encouraging the body to fidget/move around/bounce off the walls (hello sugar high) in order to burn off some of this excess energy. If for any reason your leptin was blocked, or you did not have enough leptin, the brain would not get the signal that you were full, and no matter how full your fat cells were, you would want to keep eating more!

High levels of insulin have been thought to block the leptin signal, stopping the brain from receiving the message that we are full.

Leptin resistance

Dr. Richard Johnson, from the University of Colorado has rigorously studied the subject. His research clearly shows that refined sugar (in particular fructose) is exceptionally effective at causing leptin resistance in animals, and it’s very effective at blocking the burning of fat. In the same way that you may become insulin resistant when your pancreas is chronically over producing it, so too may you become leptin resistant.

“When you give fructose to animals, they lose their ability to control their appetite, they eat more, and they exercise less. Fructose looks like it’s playing a direct role in weight gain,” he says.

According to Dr. Johnson, fructose has two effects:

  1. It stimulates weight gain through its effects on your appetite and by blocking the burning of fat
  2. It also changes your body composition to increase body fat even when you are on a caloric restriction

This is not to say that you can no longer eat fruit. Of course many contain beneficial nutrients and antioxidants. But for someone who is already obese, care should be taken to avoid high fructose fruit. Some fruits, such as lemons and limes, have minimal fructose content and are safe.

Other fruits, such as grapefruit, kiwi, and berries, also have relatively low fructose content and high levels of nutrients. However, fruit juices, dried fruits, and some fruits that are rich in fructose (such as pears, red apples, and plums) should be eaten relatively sparingly. And as fruits ripen, their sugar content increase. Have you ever noticed that a blackened banana will taste sweeter than a green one? Avoid these ripened fruits if you think fructose might be an issue for you. And above everything else – avoid fruit juices!

Can you control leptin resistance?

You can try and avoid leptin resistance in much the same way that I suggested you can control insulin resistance. Be aware of what you are eating! Avoid sugar, especially fructose (read labels and if you EVER see HFCS (High fructose corn syrup) put the product down, immediately!

Exercise will also help by stimulating cell activity and increasing muscle mass. Intermittent fasting combined with exercise in particular has been shown to have beneficial effects – this encourages you to burn your stored fat rather than the glucose you may have just eaten. Exercising first thing in the morning before eating breakfast is a great way to get this in your daily routine.

Key takeaways:

  • Insulin and Leptin work together to provide the body with energy and tell your brain when to stop eating
  • Too much fructose can cause to overproduction of leptin, and eventually leptin resistance. The brain no longer gets the ‘full’ signal, and hence thinks you are constantly starving – hello non sotp eating!
  • By sticking to a low sugar diet (including low carbs), and practising intermittent fasting, you can readjust your sensitivity to leptin.
  • Exercise is a key factor is avoiding leptin resistance.

I’ve tried to keep today’s blog short and sweet, but I want to point you in the direction of Dr Lustig’s talk on the subject. He’s a subject matter expert, and although this concept is not fully accepted, he is widely regarded in the industry of nutrition and childhood obesity. So take a look and decide for yourself. And if you didn’t see the blog from last week, you can catch up and read it here.

And now for the next part of The Hormone Series – ever heard of overactive/underactive thyroid? Know what that means? Aware of the side effects and think you could be at risk? Join me next time as I discuss Thyroxine, the metabolism controller.

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