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Why Do We Eat? A Neurobiological Perspective. Part III

In the first post, I explained that all voluntary actions are driven by a central action selection system in the midbrain (the reward system).  This is the part of you that makes the decision to act, or not to act.  This system determines your overall motivation to obtain food, based on a variety of internal and external factors, for example hunger, the effort required to obtain food, and the sensory qualities of food/drink.  These factors are recognized and processed by a number of specialized 'modules' in the brain, and forwarded to the reward system where the decision to eat, or not to eat, is made.  Researchers divide food intake into two categories: 1) eating from a true energy need by the body (homeostatic eating), e.g. hunger, and 2) eating for other reasons (non-homeostatic eating), e.g. eating for social reasons or because the food tastes really good.

In the second post of the series, we explored how the brain regulates food intake on a meal-to meal basis based on feedback from the digestive system, and how food properties can influence this process.  The integrated gut-brain system that accomplishes this can be called the satiety system.

In this post, we'll explore the energy homeostasis system, which regulates energy balance (energy in vs. energy out) and body fatness on a long term basis.

The Energy Homeostasis System

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An Encouraging Trend

I was in the Seattle/Tacoma airport today, and I noticed quite a few people taking the stairs even though they're flanked by escalators.  It's been my impression lately that more people are using stairs than even five years ago.  I used to be the only weirdo on the stairs, but today I shared them with about ten other people.  I know Seattle isn't necessarily representative of the nation as a whole, but I (optimistically) think of it as the vanguard in this respect.

One of the healthiest things a person can do is build exercise into daily life.  You don't have to be Usain Bolt or Lance Armstrong to reap the benefits of exercise.  In fact, evidence is acctmulating that moderate exercise is healthier than extreme exercise.  Taking the stairs instead of the elevator/escalator, walking or jogging even a modest amount, or standing for part of the day, can have an immediate, measurable impact on metabolic health (1).

Maybe it's macho, but I'll feel defeated the day I need a giant energy-guzzling machine to take me up a 15 foot incline.  I have legs, and I intend to use them.  Escalators are good for people who are disabled or have very heavy bags, but the rest of us have an opportunity to use our bodies in a natural and healthy way.  Part of the problem is how buildings are designed.  Humans tend to take the path of least resistance, and if the first thing we come across is an elevator, and the stairs are grimy and tucked away down some side hallway, we'll tend to take the elevator.  Architects in some places are building in more prominent stairways to encourage gentle exercise throughout the day.

Food Reward Friday

This week's lucky winner... the Hardee's MONSTER THICKBURGER!

Two 1/3 lb beef patties, four strips of bacon, three slices of American "cheese", mayo and bun.  This bad boy boasts 1,300 calories, 830 from fat, 188 from carbohydrate and 228 from protein.  Charred and fried processed meat, fake cheese, refined soybean oil mayo, and a white flour bun. You might as well just inject it directly into your carotid artery.  Add a large fries and a medium coke, and you're at 2,110 calories.  Who's hungry?  Actually I am.  

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