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Can we change our body weight?

Maybe there is that person in your life who just seems to stay naturally lean, no matter what they eat? Or always wears shorts no matter the weather? Or you may have experienced a weight loss plateau? Or lost weight and gained it back?

Now, what's all that about?!

Why and how do our bodies do this?

Why isn't it easy to change our body weight and then just stay at that body weight?

Let's explore some of the factors that control this:

Now, no one breaks the laws of thermodynamics and if someone's energy input is greater than their output, then they will gain weight, and vice versa. There are A LOT more factors at play than just calories in, calories out and therefore a mathematical equation is going to struggle to predict how a complex biological system is actually going to transfer energy.

Our bodies like stability; there is a phenomenon called 'homeostasis'. Yes, I know, science, but bear with me! Homeostasis means keeping a constant internal environment, and our body applies it to our blood sugar levels, blood acidity, body temperature etc. etc.

We see this homeostasis come into play with body weight too; we crash diet to lose weight and many, many people tend to put that weight back on again sooner or later. When people try to gain weight, this can also happen too. The body adapts to try and stay the same long term.

Mmmmm, does that mean changes in weight are impossible then?


We have way more control than we are led to believe by science, the fitness and diet industries, advertising, social media etc. We can regulate our eating and movement behaviours, and with this, we can directly influence how our genes are expressed, our metabolism etc.

Scientists have (and I wonder that their ethics panels were like!) deliberately over-fed and starved people. Let's dive in...

The Minnesota Starvation experiment is just one (pretty extreme - but in the context of WWII) example of this. Subjects were starved, limited to about half their usual daily calories and among the effects reported were irritability, depression, anxiety, fatigue, trouble sleeping, mental fog and OBSESSION with food. When allowed to re-feed and recover, some engaged with extreme overeating. (Take note: if you are always trying to lose weight and following a diet then, similar in some ways to the re-feeding effects above, restrict-binge cycles with food can be highly likely.)

When deprived of calories, humans will move less; they will fidget, tap, wander around and jiggle about much, much less. This is movement is called NEAT - non-exercise activity thermogenesis. It also includes the playing with kids, chasing after the dog, cleaning the house, climbing the stairs etc; all movement that is not exercise. Digestion will slow down as the body tries to extract as much as possible out of limited food. Our ability to produce heat (thermogenesis) will be impaired. Our RMR (resting metabolic rate) will drop. All in an attempt by the body to burn less calories.

With an excess of calories, then the reverse happens and the body RAMPS up. Our NEAT increases, so fidgeting, tapping, moving around, pacing, not sitting still, all increase. The extra energy is expended in heat and movement. The body produces more heat (do you know a human furnace?!). Digestion picks up as it doesn't have to hang onto as much food as there's a consistent intake. RMR increases.

However, individuals do this uniquely and variably.

For example, one over-feeding experiment from 2009 shows that after 8 weeks of 1000 calorie surplus, individuals gained between 0.79 lb and 9.3 lb. Yeah. So some people's brains (the arcuate nucleus region of the hypothalamus, oh yeah) can respond to excess calories and cause those people to MOVE and get HOT much more efficiently.

Interesting, huh?

Now, no matter which camp you fall in; whether you struggle or find it easy to lose or gain weight - know this...

  • Diets not working is NOT your fault

  • Your body is doing REMARKABLE things to keep you alive. It's got your back. It's on your team. Make friends with it.

  • Engaging in improving nutrition habits and more movement, in a way that suits you, WILL help you FEEL more amazing.

We CAN change our body weight; but if focusing on that is causing misery, impacting your mental and emotional well-being, or your relationships, maybe it's time to shift focus?

What do you think?

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