The Weight Loss Illusion: Understanding Why Body Fat Can Increase As Weight Decreases

Weight Loss & Diets | Written by Nathan Petitpas | Updated on 9 July 2024

A person pinching their belly fat after losing weight but noticing an increase in body fat, questioning the cause.

So, you’ve been killing it at the gym, eating your greens, drinking fat burning detox juice and protein shakes, and you’ve lost weight. However, despite the exercise, your body fat has increased.

Most people see a low body fat percentage (BFP) as the holy grail of good health and a lean body, but health and weight loss are complicated at times. If you want to decrease BFP, put an end to your frustration by following the tips below.

Understanding Body Fat Percentage

BFP is simply fat weight divided by your total weight and multiplied by 100. However, this simple formula fails to convey the array of factors that can affect BFP. This is because you can have excess body fat even at a regular or underweight BMI, putting you at risk for weight-related diseases.1

For example, your lean body mass (LBM) or skeletal muscle mass can affect your total weight, changing your BFP even if your total body fat remains the same. Hence, if you’re losing muscle mass, you might lose weight yet appear fatter! So, let’s figure out why your BFP might increase even if you’re shedding pounds.

Why You’ve Lost Weight but Body Fat Went Up

If you lost weight but body fat went up, you likely aren’t burning fat, but you might be losing weight through other means such as:

Water weight: For the first few days of a new diet or exercise regimen, you’ll likely lose a lot of water weight. This weight loss comes from decreasing your calorie intake and increasing water lost through exercise. You may end up losing up to 5 pounds of water every day!

This water loss comes mostly from sweat and going #1, so it’s essential to drink at least 2 liters a day if you’re exercising to avoid dehydration.

Glycogen stores: Glycogen is the sugar stored in your muscles and liver. Your body burns the glycogen stored within your cells for fuel in a calorie deficit. This loss of glycogen can also translate to a few pounds of weight loss.

Lowered glycogen levels can mean 0.5-1 pound of perceived weight loss every day. A gram of glycogen also comes with 3-4 grams of water, so burning glycogen adds to losing water weight.2

Muscle loss: A calorie deficit can make you lose fat, but it can also cause your body to burn muscle for fuel! Muscle loss usually happens when you’re on a very low-calorie fad or crash diet, or you’ve been dieting chronically, i.e., continuously for a long time.

Since BFP is just fat weight divided by total weight, your BFP will go up even if your body fat remains the same since you’ll only lose weight by burning muscle.

You might also lose muscle if you work out excessively but don’t eat enough protein. Protein is essential for preserving and gaining lean mass since your muscles are made primarily of proteins, so be sure to eat more of it if you’ve been working out.3

Hormone imbalance: If you consume a lot of trans fats or drink too much alcohol, it can create a hormone imbalance by lowering testosterone and promoting fat storage.4, 5 Regulate your drinking habits to manage the weight you’ve gained from alcohol, as discussed in this article on losing weight gained from alcohol.

Testosterone boosts muscle gain, which is why men generally gain muscle faster than women. Hormone disorders like PCOS can disturb your hormones and make your body store excess food as fat instead of lean mass. Consider talking to your doctor if you feel your hormones might be imbalanced.

Inaccurate body fat scales: Body fat scales can’t directly perceive your body fat – they use a mathematical formula to calculate BFP, taking into account your age, height, and gender. So, their readings aren’t the most accurate and can be off by 21% to 34%!6 Hence, you might feel like your body fat has increased even if it’s remained the same or decreased!

Try using body fat calipers instead of scales as they reduce the error range to 3-5%, letting you track your progress more accurately.7

Guideline to Lose Weight AND Get Fat % Down

What you eat and how you move are the most significant factors influencing body fat %. If you’ve shed weight but your body fat went up, you can change your diet and exercise routine to get yourself back on track!

Exercise to Get Toned & Fat Loss Will Come (Build Some Muscle)

You can increase your total weight by building muscle while maintaining roughly the same or slightly more body fat. Incorporate resistance training into your routine, as building muscle can replace jiggly fat, aiding in weight loss.

How Does Resistance Training Help?

Lifting weights creates microscopic tears in your muscles, called microtears, and your body repairs these tears by forming new muscle protein strands known as myofibrils. Eventually, these new muscle fibers increase in girth and number, causing your muscles to grow, also called hypertrophy.

As you gain weight, your body composition changes – your BFP decreases as your total weight increases without significantly affecting your body fat. Besides, strength training means your body burns extra calories long after your workout, even while resting!

What About Cardio?

Try to get in some cardio at least 2-3 times a week, too. Not only does this help you with stamina, but it also helps you directly burn fat.

HIIT or High-Intensity Interval Training can burn 25-30% more calories than LISS or Low-Intensity Steady State cardio.8 You can try HIIT workouts if you’re busy, as they tend to be only 20-30 minutes long.

However, any cardiovascular exercise will burn fat – both HIIT and moderate-intensity exercise successfully reduce body fat and waist circumference.9 Whether you jog, swim, run, dance, play sports, or walk, any cardio counts!

Remember that getting toned doesn’t necessarily mean bulking up – endurance athletes have a lot of muscle and low BFP, but they’re much skinnier than professional weightlifters. Even light weights or bodyweight resistance exercises will help you get toned.

A combination of weights and cardio will eventually give you a toned, healthy body by reducing BFP.

Eat Healthy to Lower Body Fat Percentage & Lose Weight

If you’re working out and shedding weight but your body fat still went up, you might be a chronic dieter who has plateaued from dieting fatigue. Eating very few calories for months or years means your body burns fat AND muscle for fuel, and if you’re working out, it doesn’t have enough calories to repair damaged muscles.

Low-calorie diets can create cortisol or stress hormone spikes, and if cortisol remains in your bloodstream for a long time, it can promote fat storage.10 Besides, long-term calorie restriction may also slow down your metabolism, so you plateau even while restricting.11

How Much Should I Eat to Burn Fat?

While you shouldn’t overeat, consuming enough calories to maintain your weight for a while might help you lose fat more efficiently. Taking regular breaks from restriction is essential to let your body recover from the fatigue of compensating for a low-calorie diet.

For example, if you maintain at 2,000 calories a day:

  • Eat 1,700-1,800 calories for a few weeks.
  • Go down to 1,400-1,500 for another few weeks.
  • Gradually come back to 2,000 over a month or so to reduce the diet fatigue.
  • Rinse and repeat!

When maintaining your weight (eating the calories needed to stay the same), consider intuitive eating for weight loss, focusing on fruits, veggies, and belly juice for essential nutrients without calorie counting. Sometimes it can be healthy to stop worrying about “good” and “bad” foods to give yourself a physical and mental break from dieting. This break ensures you don’t get stuck at a particular BFP.

Other Tips for Healthy Eating

Try to consume adequate lean protein like chicken breast, salmon, or plant protein instead of filling up on just carbs and fat, even if you’re bulking. People who increase their protein intake also tend to consume fewer calories effortlessly, so make an effort to eat more protein in general. You can also have a high-protein snack after working out!12

If you eat a lot of sugar and refined carbs, your body will burn the glycogen stores they form instead of fat for fuel. Try to limit these foods and replace them with fibrous fruits juices and whole-grains carbohydrates.

You don’t need to eat healthy 24/7, either – even if you eat clean 80% of your days, you’ll still lose fat and enjoy the results when you look in the mirror!

Change Your Body Composition for Good

Keep in mind that healthy BFP for men and women is 3-19% and 10-32%, respectively.13. Your body needs some fat to function, so don’t attempt to go below these healthy percentages, or you put yourself at risk for various health issues.

Other than that, if you lost weight but body fat went up, and you aren’t very far along in your journey, start small! Lift lighter weight, walk for 30 minutes a day, eat one healthy meal a day, and work up from there. Changing your body composition is a gradual but rewarding journey, and you’ll soon feel the effects with increased energy and a better mood!


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About the Author

Nathan Petitpas

Nathan has been a fitness enthusiast for the past 12 years and jumps between several types of training such as bodybuilding, powerlifting, cycling, gymnastics, and backcountry hiking. Due to the varying caloric needs of numerous sports, he has cycled between all types of diets and currently eats a whole food diet. In addition, Nathan lives with several injuries such as hip impingement, spondylolisthesis, and scoliosis, so he underwent self-rehabilitation and no longer lives with debilitating pain.