Body Fat Mass vs Body Fat Percentage
What they mean, why they matter, how to improve both
When it comes to understanding your health, weight alone doesn’t tell the full story. Two terms often thrown around - body fat mass and body fat percentage - sound similar, but they’re very different metrics. Both play a role in how you look, feel and perform, but they offer distinct insights into your body composition and, therefore metabolic health status. Here's what you need to know about each, why they matter, and how to make progress on both fronts - without falling into fad-diet traps or trending social media tactics.
What is body fat mass?
Body fat mass refers to the total weight of fat tissue in your body, measured in absolute terms - usually kilograms or pounds. Think of stepping on a smart scale that breaks down your weight into muscle, bone, water and fat. The fat portion alone is your body fat mass.
Because this number is absolute, it can increase or decrease regardless of changes in other tissues. You might gain muscle or lose water, but unless your actual fat stores change, your body fat mass remains the same.
What is body fat percentage?
Body fat percentage, on the other hand, represents how much of your total body weight is made up of fat. It’s calculated by dividing your fat mass by your total weight, then multiplying by 100. For example, if you weigh 80 kg and carry 16 kg of fat, your body fat percentage would be 20%.
This percentage is a more relative measure than fat mass, and it's influenced by changes in both fat and lean tissue. That means you could technically lower your body fat percentage without losing any fat at all - simply by building more muscle. Conversely, if you lose muscle during weight loss, your percentage could actually increase, even if you’re shedding fat.
The American College of Sports Medicine suggests healthy ranges of roughly 10 - 22% for men and 20 - 32% for women, though these ranges can vary slightly with age and activity level.
Why the distinction matters
Body fat mass gives you a direct figure: how many kilos or pounds of fat your body carries. It’s particularly useful for tracking health outcomes, since carrying excessive fat - especially around the organs - has been linked to metabolic issues, inflammation, and cardiovascular risk.
Body fat percentage, meanwhile, offers a broader picture of your physique and performance potential. Because it reflects the ratio between fat and lean mass, it’s often the go-to measure for athletes, climbers, and anyone looking to optimise how their body moves and performs, not just how much it weighs.
The benefits of reducing body fat mass
Reducing your total fat mass can unlock a wide range of health benefits. First and foremost, studies show that mortality risk rises sharply once fat mass climbs past healthy levels. In other words, carrying too much fat - regardless of your fitness level - can increase your risk of serious health issues.
Losing fat also makes movement easier. With less weight to carry, your joints experience less stress, which can improve everything from walking comfort to running efficiency. There’s also a significant metabolic advantage: as you reduce overall fat, particularly visceral fat around your organs, you improve insulin sensitivity and reduce chronic inflammation.
From a cardiovascular perspective, carrying less non-functional tissue means every heartbeat can deliver oxygen more effectively per kilogram of body weight. That means better stamina and a more efficient cardiovascular system. You may think this is exclusively beneficial to endurance athletes, but as you read this right now, you’re using your cardiovascular and respiratory system to live, therefore it makes sense to also make your system more efficient too.
The benefits of lowering body fat percentage
Lowering your body fat percentage can enhance performance in sports and improve your physique in ways that go beyond simple fat loss. When you retain or build lean muscle while reducing fat, your power-to-weight ratio improves. This makes you more efficient in nearly every physical task, from cycling and running to lifting weights or climbing the stairs at work.
A leaner body also tends to reveal the muscle definition that already exists beneath the surface. This is why strength training combined with modest fat loss can lead to dramatic visual changes - it's not always about gaining new muscle, but about uncovering what’s already there.
There are hormonal benefits too. Carrying too much fat can disrupt important hormonal signals, including testosterone, oestrogen and leptin. Getting body fat levels back into healthy ranges can help restore hormonal balance and support everything from appetite regulation to reproductive health.
For athletes in weight-class sports like boxing, rowing, or martial arts, body fat percentage is even more critical. Success often depends not just on making weight, but on having the highest possible lean mass within a weight category.
Which should you focus on?
The answer depends entirely on your goals. If you’re focused on general health or are working towards significant weight loss, then prioritising body fat mass makes sense. Reducing the total kilos of fat you carry can improve blood pressure, cholesterol, blood sugar regulation and even sleep quality.
If you’re training for performance - say, in running, cycling or climbing - then your body fat percentage becomes more relevant. Here, it’s not just about losing weight, but about maintaining or increasing muscle while gradually reducing fat. That’s what leads to a better power-to-weight ratio.
For those aiming to improve body shape or aesthetics, both metrics are useful, but often in phases. You might start with a “cut” to lower fat mass, then shift to a “build” or “recomp” phase to gain lean tissue while keeping fat levels in check.
And for people dealing with clinical issues such as sarcopenic obesity - where muscle loss and fat gain occur together - monitoring both fat percentage and lean mass is crucial. In these cases, the goal is to reduce fat while actively protecting or rebuilding muscle to reduce frailty and improve metabolic health.
In truth, most people benefit from tracking both metrics, at least initially. What’s important is to choose the one that aligns most closely with your immediate objective and use the other as a secondary measure to keep your progress balanced.
How to reduce fat mass & percentage - without gimmicks
The good news is that improving both body fat mass and percentage doesn’t require drastic diets or questionable supplements. It just takes a focused approach to three key areas: nutrition, training, and lifestyle.
From a nutritional perspective, the goal is to create a modest calorie deficit - typically around 10 to 20% fewer calories than your body needs to maintain weight. Larger percentage deficits can backfire, increasing hunger and the risk of losing more muscle tissue than you otherwise would on the more conservative 10-20%.
Protein plays a central role in this process. Aiming for around 1.6 to 2.2 grams of protein per kilogram of body weight helps preserve muscle and increases satiety, making it easier to stick to your plan. Research shows that higher protein diets can result in several kilos of fat loss over just a few months, without sacrificing lean tissue. In some studies, this was also shown - albeit to a lesser extent - in individuals who didn’t do any resistance training at all!
Focusing on whole and minimally processed foods can also make a big difference. They tend to be more filling per calorie and help you manage hunger naturally. A simple rule of thumb is the 80/20 plate: fill most of your meals with lean proteins, vegetables, and healthy fats, and leave room for some flexibility with foods you enjoy.
Carbohydrate timing is another useful strategy - eating more carbs on hard training days and less on rest days can fuel workouts without leading to a chronic energy surplus. Anecdotally, there are some people who simply don’t get on well without added carbs on their training days. Experiment a little, there’s no rush to figure out what works for you.
When it comes to training, combining resistance work with cardiovascular sessions is the most effective approach. Strength training two to four times per week helps stimulate muscle growth and prevents the losses that often accompany dieting. Focus on multi-joint exercises like squats, presses and rows, and aim to gradually increase the load or reps over time.
High-intensity interval training (HIIT) can be added two to three times per week. Short bursts of intense effort, followed by recovery periods, have been shown to reduce both fat mass and fat percentage while preserving or even increasing lean mass. Think bike sprints, hill intervals or kettlebell circuits.
Low-intensity steady-state cardio (LISS), like brisk walking, swimming or cycling, also has its place - especially on recovery days. These longer, easier sessions increase your weekly calorie burn without adding too much stress to the nervous system.
It should be noted that much like the carbohydrates on training days scenario, equally there is an individualistic approach to be taken to training too. More specifically any form of cardiovascular training, as an example my hunger goes through the roof if I perform any interval based training whilst in a calorie deficit, so I would personally opt for LISS. I have first-hand seen this to be the opposite in some clients I have worked with over the years. Try each out for yourself and see what works well for you.
Lifestyle habits can’t be ignored either. Sleep is a powerful ally in fat loss, with poor sleep linked to increased belly fat and disrupted appetite hormones. Aim for seven to nine hours a night. Managing stress is also essential, as chronically elevated cortisol can lead to stubborn fat storage, particularly around the midsection. Simple habits like breathwork, mindfulness, or even regular outdoor walks can help manage your stress load.
Alcohol is another factor worth considering. It provides 7 calories per gram, lowers your inhibitions around food and blunts the body’s ability to build muscle. A few drinks here and there are unlikely to derail progress, but nightly pints might. With the rise of non-alcoholic beverages and even adaptogenic beverages, this has become a little easier - even beneficial - in latter years.
Finally, everyday movement matters more than people realise. Non-exercise activity thermogenesis (NEAT) refers to all the calories you burn from walking, standing, fidgeting and other daily actions. It can account for hundreds of calories burned per day. Aiming for 8,000 to 12,000 steps a day or taking a short walk after each meal can be surprisingly effective.
How to track progress
Tracking your progress doesn’t have to be obsessive - it just needs to be consistent. Weighing yourself daily at the same time and averaging the results over a week helps smooth out fluctuations caused by water and food intake.
Every couple of weeks, taking waist or hip measurements (depending on your sex) can give you a clearer picture of changes in visceral fat. Body composition scans - whether via DXA, bioelectrical impedance or callipers - are best spaced 6 to 12 weeks apart. They won’t be perfect, but they do show trends over time, which is what really matters.
Final thoughts
Body fat mass tells you how much fat you carry. Body fat percentage tells you how much of your body is made up of fat in relation to everything else. Both are useful and both matter.
Reducing fat mass improves your health. Lowering fat percentage helps with performance and aesthetics. Which one to prioritise depends on your current goal, but most people see the best results by focusing on the fundamentals: eat in a modest calorie deficit, get enough protein, strength train regularly, add some cardio, prioritise sleep and stay active every day.
You don’t need extreme diets or high-tech gadgets to make progress. You just need a plan, consistency, and the patience to let the numbers on the scale and in the mirror move in the right
