The Science of Fat Burning: How to Reduce Belly Fat and Improve Metabolic Health

When people talk about “fat burning,” they often imagine one single type of body fat — but body fat isn’t just one thing. In reality, the body stores fat in different places, and those storage sites don’t carry the same risks for your health. The two most important to understand are subcutaneous fat and visceral fat:

Subcutaneous Fat

Found under the skin and serves as an insulation & energy storage. It is usually located in the arms, thighs, glutes, and abdomen. It is also the main fuel source as the body uses oxygen during any moderate exercise that lasts for over 2 minutes at a time.

Visceral Fat

Stored deep around abdominal organs including the liver, pancreas, and intestines. Visceral fat is strongly linked to insulin resistance, type 2 diabetes, and cardiovascular disease.

—

There are 2 types of nutritional fat that can be detrimental to our health if eaten in excess and consistently; saturated fats and trans-fats (read ‘Re-thinking Fat in the Age of Mis-Information’). Besides this, excess sugar & simple carbohydrates can also affect how and where fat is stored. Let’s break this down further.

Saturated Fats

Sources: butter, fatty cuts of meat, cheese, coconut oil, etc.

Mechanism: If the energy from saturated fats you consume is not burned efficiently, it will convert to fat storage.

Effects:

• Excess consumption raises LDL (bad) cholesterol, especially small dense LDL which stimulates plaque formation in the arteries.

• Promotes general weight gain (subcutaneous fat) and the accumulation of visceral fat.

• Impairs insulin sensitivity when over-consumed.

Trans-Fats (artificial, partially hydrogenated oils)

Sources: processed snacks, cakes, cookies, pastries, vegetable/sunflower oil fried food, etc.

Mechanism: Interfere with normal fat metabolism and promote fat storage; where the body alters how the body partitions fat.

Effects:

• Strongly increases visceral fat (pushes fat more to the belly/organ region than the skin).

• Raises LDL cholesterol and lowers HDL cholesterol simultaneously (worst of both worlds).

• Triggers systemic inflammation → higher risk of heart disease.

• Promotes fatty liver (ectopic fat storage in the liver).

Sugar & Simple Carbohydrates (glucose, fructose, sucrose, refined flour products)

Sources: fruit juice from concentrate, fizzy drinks, pastries, white bread, chocolate, sweeties, etc.

Mechanism: Rapid blood sugar spikes, insulin rises which signals the body to store excess energy as subcutaneous fat. Also once glycogen stores are full, excess glucose is converted into triglycerides in the liver. These triglycerides are then stored as subcutaneous fat.

Effects:

• Spikes insulin, which favours fat storage and weight gain and reduces fat burning efforts.

• Excess consumption can increase risks of high blood pressure and type-2 diabetes.

• Excess fructose consumption primarily metabolised in the liver, strongly contributes to visceral fat and nonalcoholic fatty liver disease.

The good news is, both types of body-fat can be reduced naturally without medicine — but they respond differently depending on the strategy you decide to use.

Subcutaneous fat is largely about consistent calorie burn and exercise over time, while visceral fat is more sensitive to lifestyle shifts like Intermittent Fasting, HIIT Training, consistent physical activity, varying your intake of fruits, vegetables and whole foods, while cutting down on processed sugars and unhealthy fats.

--

Intermittent Fasting

Intermittent Fasting isn’t a “magic trick” for weight loss — it works because of how it changes your body’s fuel system.

Normally, when you eat, your body uses glucose (sugar) from the food as energy. Insulin, a hormone, helps store any extra energy as fat.

When you fast, insulin levels drop, and your body shifts from storing energy to burning stored fat for fuel.

This process benefits both subcutaneous fat (the fat under your skin) and visceral fat (the fat around your organs), but in slightly different ways:

• Subcutaneous Fat:
  
  When you fast, your body breaks down stored fat into fatty acids, which are then used for energy.
  
  Over time, this leads to a gradual reduction in the “pinchable” fat under the skin.

• Visceral Fat:
  
  Visceral fat is more responds faster to hormonal changes. Fasting lowers insulin and increases fat-burning hormones like adrenaline and growth hormone, therefore visceral fat often reduces quicker than subcutaneous fat.
  
  This is why ‘Intermittent Fasting’ is linked not just to weight loss, but also to better blood sugar control, reduced liver fat, and lower risk of metabolic diseases.

HIIT Training

High-Intensity Interval Training (HIIT) is a workout style where you alternate short bursts of intense activity (like sprinting or cycling hard) with brief rest or lower-intensity periods.

This style of training is especially powerful for fat loss because it pushes your body to burn calories not just during the workout, but also for hours afterward — a phenomenon called the “EPOC” (Excess Post-Exercise Oxygen Consumption).

By rapidly increasing energy demand and triggering hormones like adrenaline and growth hormone, subcutaneous fat is broken down into fatty acids which is used as fuel for exercise.

Here’s how it affects different types of fat:

• Subcutaneous Fat:
  
  HIIT burns a large number of calories in a short time and boosts your metabolism afterward, making it highly effective for reducing the fat under the skin - especially around the belly, arms, and thighs.
  

• Visceral Fat:
  
  Research shows HIIT is particularly effective at reducing visceral fat, even more than some steady-state cardio.
  
  Like Intermittent Fasting, HIIT training spikes in adrenaline and growth hormone, which promotes fat burning. Regular HIIT sessions can significantly shrink belly fat around the organs, lowering risks of diabetes, heart disease, and fatty liver.

Whole Foods, Fruit & Veg

Eating a diet built around whole foods (e.g. whole grains, fruits, vegetables, nuts, and seeds) is one of the simplest and most effective ways to reduce excess body fat.

Unlike processed foods, whole foods are nutrient-dense, higher in fibre, and usually contain natural sugars as well as unsaturated & saturated fats. This combination helps control hunger, balance blood sugar, and support fat loss.

Here’s how it affects different types of fat:

• Subcutaneous Fat:
  
  Whole foods are less calorie-dense and keep you fuller for longer, which helps prevent gluttony (overeating). Fibre from fruits and vegetables slows digestion, reduces cravings, and lowers calorie intake over time.
  
  This steady calorie control helps reduce the fat stored under the skin.
  

• Visceral Fat:
  
  Replacing refined carbs, sugars, and trans-fats with whole fruits, vegetables, and minimally processed ingredients, lowers insulin spikes and inflammation — which prevents visceral fat storage.
  
  Following a minimum 6-week lifestyle change, this shift can significantly reduce the fat that builds up around your organs and improves metabolic health.

Bringing It All Together: The Optimal Strategy for Fat Loss

The most effective way to reduce both subcutaneous fat (under the skin) and visceral fat (around the organs) is to combine smart eating habits with strategic exercise (in other words, a combination of all three).

• Intermittent fasting helps your body switch into fat-burning mode by lowering insulin and tapping into stored fat, with especially strong effects on visceral fat.
  

• HIIT training creates a powerful calorie burn during and after workouts, shrinking subcutaneous fat while also targeting stubborn belly fat around the organs.
  

• A whole-foods diet rich in fruits and vegetables prevents new fat buildup by stabilising blood sugar, reducing inflammation, and controlling hunger naturally.
  

Together, these approaches complement each other: fasting makes your body more efficient at burning fat, HIIT accelerates fat loss and improves fitness, and a whole-foods diet keeps fat from creeping back in.

If your goal is not just to look leaner but to also protect your long-term health, combining intermittent fasting, HIIT workouts, and a diet based on whole foods, fruits, and vegetables is one of the most effective and sustainable ways to reduce both subcutaneous and visceral fat.

If you have serious goals concerning your health, body size, or confidence and would like to implement these optimal ways of conditioning your body for health and dropping unnecessary body fat, book in a 1-2-1 consultation with me and lets get to work!

Lifestyle Consultation

Online or In Person - Book a 1-2-1 now!

Consultation Package

2 Trial PT Sessions

Lifestyle Consultation

45 Minute Consultation