Muscle weighs more than fat, so if you've been hitting the gym and building lean muscle mass, you may weigh more than someone who appears to have a similar body shape but lacks muscle tone. Another factor to consider is water weight.
Muscle tissue is denser than fat, which means that even if you have a higher weight, you may still look leaner because muscle takes up less space (1). So, if you have a higher muscle mass, it can contribute to a heavier weight without necessarily looking fat. Muscle vs. Fat: Muscle and fat have different densities.
Why Do Some People Eat So Much But Don't Get Fat? Our tendency to gain or maintain body weight is complex, genetics, nutritional and behavioural factors all play a role. The extent to which each of those factors affects our weight varies, according to the individual.
So even though you may be losing fat, you're gaining muscle. You might feel slimmer, even as the number on the scale rises. “The scale doesn't tell the entire story,” said exercise physiologist Christopher Mohr, PhD, RD. “Since muscle and fat take up different volume, they look very different on the body.”
The difference is that muscle is more compact than fat, which means that it takes up less space... However, the same mass of muscle weighs more than the same mass of fat, which may explain why you appear thinner but weigh more.
Since dense muscle tissue takes up less space than fat, it's possible you may weigh the same (or even more) yet appear slimmer than another person with the same weight, a similar height and frame because of the difference in your body composition.”
Muscle weighs more than body fat
This means that muscle and fat may look the same on the scale, but they'll look different on your body. While your clothes may feel looser, the scale may tell you otherwise. Count this as a win.
The rule of thumb, Fernstrom says, is that losing 8 to 10 pounds translates to going down one size. Still, if you lose "up to 15 pounds, you may be OK in your old size," she says. But putting off buying new clothes until you really need them doesn't work for everyone.
If you're asking yourself, “Why am I gaining weight when I barely eat,” several factors may be at play. Your body may be holding onto fat stores if your eating habits are inconsistent or restricted. Or, your weight gain may be the effect of a sedentary lifestyle, medical condition, or long-term stress.
Fluid retention
It's totally normal for your weight to change up to four pounds in a single day, based on your fluid levels. Fluid retention, or edema, is when a lot of fluid builds up in the body. This can cause a sudden weight gain of 15 or more pounds.
But as a general rule, normal weight gain is: About 5 pounds per year between ages 2 and 5. About 5-10 pounds per year for school-age children.
However, BMI cannot differentiate between body fat and muscle mass. This means there are some exceptions to the BMI guidelines: Muscles – body builders and people who have a lot of muscle bulk will have a high BMI, but are not overweight.
Similarly, you may notice increased muscle definition, less softness, and an overall leaner physique. Checking in on how your clothes fit can be another useful rule of thumb. Since muscle is denser than fat, if you've gained weight but your clothes fit a little looser, that's a good sign you may have gained muscle.
Muscle is denser than fat, meaning a kilogram of muscle takes up less space in your body than a kilogram of fat. So, even if you gain muscle and your weight on the scale increases slightly, you can appear slimmer and more toned.
“Your skin is the largest organ in the body and absorbs fluid easily,” says Dr. Keith Kantor, a leading nutritionist and CEO of the Nutritional Addiction Mitigation Eating and Drinking (NAMED) program. “After a swim or a shower, your body can absorb 1 to 3 cups of water, increasing your true weight by a few pounds.”
Aim to weigh yourself on the same day, at the same time and in the same environment each week – for example, first thing every Friday morning when you're getting ready to take a shower, after you've gone to the bathroom, but before you've drunk or eaten anything.
Water weight is not usually a cause for concern, but it can be uncomfortable and recurring. Reducing salt and carbohydrate intake, keeping hydrated, and frequently exercising are all good ways to lose water weight and prevent it from returning.
If your weight has increased within a day or two, it's unlikely that it's fat. Weight gain caused by fat happens gradually when you consume more calories than you burn off. If the weight is mostly around your tummy, ankles and fingers, the chances are, it's down to water retention.