Fat: The Most Misunderstood Part of Your Body – What Really Happens When You Lose Weight 

Have you ever wondered how do I lose body fat and what actually happens when we shed those extra pounds? It’s a question that rarely crosses people’s minds. Most assume that fat simply gets burned off, or that it exits through our urine or faeces. However, the science tells a very different and fascinating story. 

Fat often gets a bad reputation, but understanding how it works in your body can be a game-changer. Today, I’m going to clear up misconceptions about fat cells, weight loss, and why keeping weight off can be so challenging. I’ll also share practical tips on ‘how do I lose body weight’ to shrink those fat cells and maintain a healthy lifestyle.  

As a nutritionist and food scientist, I discuss these details with our clients to help them better understand weight management. So, let’s demystify the process and explore the real science behind the perennial question How do I lose body Fat’. 

The Basics: How Fat is Stored 

Before we tackle ‘how do I lose body fat’, it’s important to know how fat is stored. Fat is stored in cells called adipocytes (pronounced A-duh-pow-sites). These cells contain triglycerides – molecules formed from excess calories that your body didn’t use for immediate energy. Interestingly, the number of adipocytes you have is largely set during childhood and adolescence. When we gain weight, these cells don’t multiply; instead, they expand to accommodate more fat. 

This means when we lose weight, the fat cells don’t disappear – they simply shrink. Think of them like balloons inflating and deflating. This insight helps explain why maintaining weight loss can be tricky. Your existing fat cells are always ready to store more if you consume excess calories. 

The Process of Fat Loss: It’s All About Exhaling 

So, how do I lose body fat effectively? When we lose weight, our body breaks down triglycerides for energy. This process produces carbon dioxide (CO₂) and water (H₂O) as by-products. 

• Carbon dioxide is expelled when you breathe out. 

• Water exits through sweat, urine, and even breath moisture. 

• According to research from the National Institutes of Health (NIH), a staggering 84% of fat loss occurs through breathing out carbon dioxide (source: National Institutes of Health). The remaining 16% leaves as water. In other words, most of the fat you lose literally leaves your body when you exhale! 

• This is one reason exercise plays a crucial role in weight loss. The more you move, the more you breathe, and the more carbon dioxide you expel. Whether it’s a brisk walk, a yoga session, or a high-intensity workout, focusing on deep, steady breathing can help maximise fat loss. 

Why Exercise Matters for Fat Loss 

When people talk about “fat-burning” exercises, they’re not entirely wrong – but the term is misleading. You’re not setting fat on fire; you’re breaking down triglycerides and expelling the resulting carbon dioxide and water. 

During exercise, your body requires more energy, which prompts the breakdown of fat stores. The harder you work, the more carbon dioxide you exhale. This is why aerobic activities like running, cycling, and swimming are particularly effective for weight loss. They encourage deeper and faster breathing, helping you get rid of fat more efficiently. 

But it’s not just about intense workouts. Even gentle activities According to research from the National Institutes of Health (NIH), a staggering 84% of fat loss occurs through breathing out carbon dioxide (source: National Institutes of Health). The remaining 16% leaves as water. In other words, most of the fat you lose literally leaves your body when you exhale! 

This is one reason exercise plays a crucial role in weight loss. The more you move, the more you breathe, and the more carbon dioxide you expel. Whether it’s a brisk walk, a yoga session, or a high-intensity workout, focusing on deep, steady breathing can help maximise fat loss. 

Do Fat Cells Ever Go Away? 

Unfortunately, no. Once fat cells are created, they don’t disappear – they simply shrink when you lose weight. Research from Yale University shows that fat cells can be generated quickly when consuming a high-fat diet, and dieting can only shrink them, not eliminate them entirely source​ YaleNews 

This is why yo-yo dieting – losing and regaining weight repeatedly – can be problematic. Fat cells seem to have a “memory” and can easily re-expand if old eating habits return. This phenomenon makes long-term weight maintenance challenging. 

Exercise like walking or stretching can contribute to fat loss over time – as long as you’re consistent. 

Sleep and Fat Loss: The Overnight Effect 

Here’s something you might not know you’re still losing fat while you sleep. In fact, a significant amount of fat loss happens during deep sleep when your body is repairing itself and maintaining essential functions. Your breathing rate remains steady, and you continue to expel carbon dioxide. 

Good quality sleep also helps regulate hormones like leptin and ghrelin, which control hunger and fullness. Disrupted sleep can interfere with these hormones, leading to overeating and weight gain. So, prioritising sleep is crucial for maintaining a healthy weight. 

How to Make Fat Cells Shrink Effectively 

Since fat cells don’t disappear, the goal is to manage their size. Here’s how you can lose body weight – support healthy, sustainable weight loss: 

1. Balanced Diet: Focus on whole, nutrient-dense foods that promote satiety and boost metabolism. 

• Include lean proteins (chicken, fish, legumes). 
• opt for healthy fats (avocado, nuts, olive oil). 
• Prioritise high-fibre foods (vegetables, whole grains) to improve digestion and keep you full longer. 

Explore this further in my Your Gut Health, Microbiome & Nutrition Masterclass at The Cooking Academy to learn how to prepare meals that nourish and sustain you. 

2. Regular Exercise: Incorporate both aerobic activities (walking, cycling) and strength training. Exercise not only burns calories but also increases muscle mass, which helps boost your resting metabolism. 

3. Mindful Eating: Pay attention to hunger and fullness cues. Slowing down during meals helps prevent overeating. 

4. Sleep Well: Prioritise 7-8 hours of quality sleep. Poor sleep affects hormones like ghrelin and leptin, which control hunger and satiety.  Book a presentation on The Science of our Sleep here for your next work wellness event.

5. Manage Stress: Chronic stress increases levels of cortisol, which can lead to fat storage, particularly around the abdomen. 

Recommended Foods for Sustainable Weight Management 

Here are some specific foods to help shrink fat cells and maintain a healthy weight: 

• Leafy Greens: Spinach, kale – high in fibre and low in calories. 

• Fatty Fish: Salmon, mackerel – rich in omega-3 fatty acids, which help reduce inflammation. 

• Nuts and Seeds: Almonds, chia seeds – provide healthy fats and protein. 

• Berries: Blueberries, strawberries – rich in antioxidants and fibre. 

• Legumes: Lentils, chickpeas – excellent sources of protein and fibre. 

For a hands-on approach, join my Your Gut Health, Microbiome & Nutrition Masterclass here to learn how to incorporate these foods into your daily routine. 

Why Preventing Weight Regain Is Key 

Once fat cells shrink, keeping them small is crucial. Remember that fat cells are eager to expand if you return to old habits. Consistency in diet, exercise, and lifestyle is your best defence. As researchers at Yale note, while we can’t eliminate fat cells, we can control their size by making sustainable lifestyle choices source​ 

YaleNews 

Key Takeaways 

• Fat loss primarily happens through breathing. About 84% of fat is expelled as carbon dioxide, and 16% as water. 

• Fat cells don’t disappear when you lose weight – they shrink. This makes maintaining weight loss challenging. 

• Exercise boosts fat loss by increasing your breathing rate and expelling more carbon dioxide. 

• Good sleep supports hormone balance and fat loss. 

• If you’re wondering how do I lose body fat, remember: you’re literally breathing it out! 

References 

• National Institutes of Health (NIH): Link to NIH research 
• University of New South Wales: Link to UNSW research 
• Yale University: Link to Yale research 
• Harvard Medical School: Link to Harvard research 
• King’s College London: Link to King’s College research 
• Oxford University: Link to Oxford research 

Additional Resources 

• Where Does Fat Go When You Lose Weight? – UNSW​ 
• The University of New Mexico 
• Yale Study on Fat Cells​ 
• YaleNews 
• The Role of Exercise in Fat Loss – Harvard Health​ 
• Texas A&M University-Corpus Christi 
• Mindful Eating Guide – NHS​ 
• The University of New Mexico 

Kumud Gandhi

Kumud Gandhi is a Nutritional Food Scientist bestselling Author, Broadcaster, and Keynote Speaker on the subject of nutritional health for productivity & performance in the workplace.  In 2010 Kumud founded ‘The Cooking Academy’ a cookery school that focusses on cooking for nutritional health and wellbeing.  Kumud regularly presents to international audiences on a variety of topics such as ‘Eating for Immunity and a Lifetime of Wellness’. She is an expert in the field of Wellness in the Workplace and works with organizations to create transformational change in employee health & well-being through nutrition and health coaching.