Body Fat: How To Check It & How To Lose It

Updated: May 12, 2021

A spare tyre, the flabby bits, a muffin top, junk in the trunk. Whatever you call it excess body fat can be detrimental to your health and increase your risk of disease. Everyone wants to feel happy and beautiful in their skin but it is important to not let being body positive get in the way of being healthy. This is not ‘fat shaming’ or bullying. This is about giving you the facts and advice you need to lower your risk of disease and be as healthy as possible. But what exactly is body fat for? How can you see how much you have? And how can you get rid of excess fat? These are the questions we’ll answer in this post and more.

What Is Body Fat?

The foods and drinks you consume are converted into energy through digestion to drive all the physiological processes going on in your body. If you eat more than you need, your body converts any excess into body fat, which is then stored within your fat cells around your body for later use. Fat is stored in 2 different places, under the skin (a.k.a. subcutaneous fat) and around the organs (a.k.a. visceral fat). Subcutaneous fat is the fat most people worry about because it covers the muscles and prevents them from having that toned, lean, healthy appearance. However, subcutaneous fat is generally quite low risk to your health. On the other hand, visceral fat is the fat you don’t see, it sits around your organs and is much more dangerous to your health. It is important to know the difference between the 2 types as some methods for assessing body fat levels can only measure subcutaneous fat and may not give an accurate indication of how much body fat you have. Regardless of whether the fat is stored under the skin or around the organs, fat is typically stored in fat cells. The number of fat cells you have is usually fixed on reaching adulthood but how much fat is within each cell can fluctuate greatly. When you rapidly lose weight and then binge out afterward (e.g. when you slim down for a holiday then eat in excess all week), you can trigger the growth of new fat cells, which can make dieting harder in the future. In obese populations, fat can completely fill the cells and fat deposits can start to occur outside of fat cells in random locations around the body. This is why some very large people may have more fat on their belly, or on their thighs, or on their arms, or just about anywhere. I have even seen excess fat deposits in a person’s forehead!

When you lose body fat you keep the same number of fat cells but they will shrink down in size. When fat cells shrink they increase the hormone leptin (a.k.a. the hunger hormone), causing you to feel more hungry and more tempted by food cravings. The ability to store energy for later use is an evolutionary advantage to help survive droughts and famine. However, in the western world, droughts and famine are not a concern and our access to food is 24/7. Nature though hasn’t had time to catch up with this and the backup system for storing fat has not changed. Your capacity to store fat is unlimited and why people can grow to insane sizes. That’s why the world’s heaviest person was able to get to a staggering 635 kg (1,400 lbs)! Now that you know what body fat is for and why you can store so much of it, it’s time to look at ways you can measure your body fat percentage so you can stay in the best of health and/or enhance your performance.

How Do You Measure Body Fat?

There are a number of methods for measuring body fat including tape measure girths, bioelectrical impedance (used in labs, medical centres, gym, and home scales), skinfold calipers (used mostly by personal trainers and sport scientists), hydrostatic weighing or air displacement techniques (used by sports teams and scientists), and DEXA or MRI (favoured by bodybuilders and the gold standard in body composition measurements).

Height to Weight Ratios (i.e. BMI)

Estimating a healthy weight from BMI calculations can be a good guide for most people who are not very active with larger than average amounts of muscle mass. However, trying to calculate an accurate estimate of body fat from a height to weight ratio is not possible.

Chart courtesy of


Measuring the girth of key areas of the body can be an accessible method for estimating your body fat levels that requires no expertise and no specialist equipment. These girth measurements are then used to calculate your estimated body fat percentage or track weight loss/muscle gain progress. However, body fat calculations using these types of measurements can be easily skewed in those who are engaged in high amounts of cardiovascular exercise or have much higher levels of muscle mass. Measurements include: