Metabolism Isn't What You Think. Why Physics Matters

I spent Friday afternoon with Robert Fosbury, a physicist and astrophysicist who's worked on the Hubble Space Telescope and studied how galaxies form. Now he's applying physics principles to human biology.

Physics is new territory for me. I'm currently studying quantum biology in the US, trying to understand how light and energy work at a cellular level. I'm very much learning.

I'm beginning to understand why physics matters in biology. And it's changing how I see metabolism completely.

We talk about our bodies through biology and chemistry. Hormones, nutrients, cellular processes. I do the same in clinic every day. All true, all important.

But we're also physical systems operating under the same laws as everything else in the universe. Thermodynamics. Energy transfer. Entropy.

These aren't abstract concepts. They govern how your cells work, how your mitochondria produce energy, how your body maintains order against constant chaos.

Robert's background gives him a different way of seeing metabolism. We talked about photometabolism—how light directly affects metabolism. I'll explain that another time. But first, entropy.

Entropy: The First Physics Lesson

Here's the concept that kept coming up: entropy.

Think about cooking a meal. You create something nutritious and organised, that's order. But you also create dirty pans, heat, mess in the kitchen, that's disorder. You can't have one without the other.

That's entropy. Creating order in one place requires creating disorder somewhere else.

Your body does this constantly. Building proteins, repairing cells, maintaining temperature, all highly organised processes. But each one generates waste: heat, carbon dioxide, metabolic byproducts that need removing.

This isn't a flaw. It's physics. The second law of thermodynamics in action.

Your Body Needs to Export Disorder

Your cells maintain incredible organisation. Proteins folding precisely. Signals firing on time. Systems communicating. That's order.

But maintaining that order creates disorder that has to go somewhere. Your body exports it as heat, through breath, through waste. When this export system works well, you feel energised. When it doesn't, disorder accumulates internally.

This is where food type matters.

Processed Foods Deliver Pre-Existing Disorder

Whole foods arrive with intact structures. Long carbon chains. Fibres. Your body systematically breaks these down, extracting energy and exporting the disorder as heat through digestion.

The thermic effect of food, the energy spent processing what you eat, is your body's entropy export system. For example whole foods might use say 140 calories to process an 800-calorie meal. That heat generation is disorder leaving your system.

Processed foods have already been broken down during manufacturing. Structures fragmented. The disorder already created. When you eat them, your body receives pre-disordered fuel!

Less processing required means less heat generated. About 75 calories for the same 800-calorie meal. Less entropy export. More disorder accumulating internally breaking down the system and function.

What This Means Practically

You eat processed foods. Blood sugar spikes because the natural structure and fibre are stripped away, so glucose rushes in fast. Cells scramble to manage the chaos. Insulin surges, and energy is pushed into storage, often as fat, because the system cannot burn it all efficiently in that moment.

Over time, your mitochondria generate more oxidative “waste” and stress relative to clean, usable ATP from the same calories. Then comes the crash, then the craving, and the cycle repeats.​​

Whole foods: steady glucose, efficient energy, controlled heat that exports disorder outward. Your cells maintain order without metabolic chaos.

And we're not even discussing nutrient density yet! We know processed foods lack vitamins and minerals. But they also lack structural order, delivering pre-existing disorder that creates metabolic chaos.

Why This Matters

Understanding your body through physics changes how you think about metabolism. It's not just biochemistry, it's energy systems, thermodynamics, physical laws.

And this is just the beginning. Much more to come.

Physics applied to biology. It's fascinating.

What You Can Do

• Choose foods that still look like they grew (intact structures your body processes) - whole foods (typically they don't contain a barcode!) - be honest with yourselves assess your foods - how much of what you eat is processed?

• Prioritise protein and natural fat at meals (steady energy, not spikes)

• Notice warmth after eating (entropy export working)

• Move after meals (mechanical work helps disorder exit)

P.S. If this made you think differently about food, forward it to someone who might find it useful. And reply if you want. I'm curious what resonated.

The information provided by Sarah Bayliss, A Registered Nutritional Therapist, is for educational purposes only. It is not a substitute for professional medical advice. Always consult your healthcare provider before making any dietary or lifestyle changes.