If you want to change your body composition, boost energy, or perform better in the gym, understanding your metabolism is key.
Metabolism isn’t just about how “fast” or “slow” you burn calories, it’s the series of chemical processes that turn your food into usable energy.
Let’s break down what actually happens when you eat, move, and recover.
The 5 Steps to Metabolising Food into Energy
There are five key stages that convert food into energy, and they all happen inside your body every single day.
Step 1: Digestion & Absorption
This is where it all begins. Food is broken down in your gut into usable nutrients.
To do this effectively, your body needs stomach acid, digestive enzymes, and a healthy microbiome, which is why gut health directly affects your metabolic rate.
Step 2: Glycolysis (Carbs → Quick Energy)
Carbohydrates are your body’s preferred fuel source because they’re easy to convert into energy.
1 gram of carbs = 4 calories of energy.
Glucose (from carbs) breaks down into pyruvate, releasing ATP (the body’s energy currency).
This process fuels your muscles and brain and is exactly why fuelling before training matters. You’ll train harder and burn more calories when your body has what it needs.
Step 3: Beta-Oxidation (Fats → Sustained Energy)
Fats provide slow, steady energy, 1 gram gives 9 calories.
Fatty acids are broken down into acetyl-CoA, releasing large amounts of ATP.
This is your body’s endurance engine, think long workouts or steady energy between meals.
Step 4: Deamination (Protein → Backup Energy)
When carbs and fats run low, your body can use protein for energy.
Amino acids are stripped of nitrogen and converted to energy intermediates.
This happens during fasting or very low-calorie diets, which is why extreme calorie restriction slows progress, you burn protein instead of using it to rebuild and repair muscle.
Step 5: Krebs Cycle & Electron Transport Chain (The Energy Factory)
This is where everything comes together.
The Krebs Cycle and ETC produce the bulk of your body’s ATP, the usable energy that powers every cell, movement, and thought.
Catabolic vs. Anabolic Metabolism
Everything above falls under catabolic metabolism, the breakdown of nutrients to release energy.
Once that energy is available, your body shifts to anabolic metabolism, where it uses that energy to build and repair.
Catabolism = Energy-releasing (breakdown)
👉 Happens during exercise and fat loss.
Anabolism = Energy-consuming (building)
👉 Happens during recovery, muscle growth, and repair.
You have an “anabolic window” right after exercise - roughly 30–45 minutes - where eating 20–30g of protein supports muscle repair and recovery. That’s your post-workout fuel sweet spot!
Meet Your Metabolic Hormones
Your metabolism is guided by three key hormones, Leptin, Ghrelin, and Insulin.
Leptin: The Appetite Regulator
Produced by your fat cells, Leptin tells your brain you have enough stored energy.
When levels are high, you feel full; when low, you feel hungry.
Helps control appetite and fat storage
Supports long-term energy balance
Signals the brain: “We’ve got enough, stop eating.”
What affects it:
High body fat = higher leptin (but risk of leptin resistance)
Dieting or low body fat = lower leptin (increased hunger)
Lack of sleep and skipping meals can also reduce leptin response
To support leptin balance:
Eat regularly (every 3 hours during your eating window)
Hit your daily calorie needs (not under BMR)
Prioritise protein and adequate sleep
Ghrelin: The Hunger Hormone
Produced in the stomach, Ghrelin tells your brain when it’s time to eat.
It rises before meals and falls after eating.
What affects it:
Fasting or skipping meals increases ghrelin
High-protein, high-fiber meals keep ghrelin low (you stay fuller longer)
Lack of sleep raises ghrelin, making you hungrier
To keep ghrelin in check:
Eat balanced meals regularly
Prioritise protein + fiber
Aim for 7–9 hours of sleep
Avoid fasted training unless it’s early morning and you’ve eaten well the night before
Insulin: The Storage & Growth Hormone
After eating, especially carbs, insulin rises to move glucose into your cells for energy or storage.
It also helps shuttle amino acids into muscles, supporting growth and recovery.
What affects it:
High-carb or processed meals spike insulin
Regular exercise improves insulin sensitivity
Overeating and inactivity can cause insulin resistance, leading to fat storage and fatigue
To maintain healthy insulin levels:
Focus on whole, unprocessed carbs
Exercise consistently
Manage stress (high cortisol affects insulin sensitivity)
Include protein with each meal to stabilise blood sugar
Putting It All Together
Metabolic conditioning isn’t just about burning calories, it’s about creating balance between fueling, training, recovery, and hormones.
To get the most out of your metabolism:
Eat a balanced diet with the right macronutrient ratios
Fuel before training and recover after
Sleep well and manage stress
Don’t under-eat, your body needs energy to burn energy
Your metabolism isn’t broken, it just needs the right inputs.
When you fuel it properly, you’ll perform better, recover faster, and see lasting results.
