Understanding Weight Loss vs. Fat Loss

Ahh, the scale. How is it that an inanimate object has such incredible power to affect our mood and our self-esteem? The truth is that we are much more vulnerable to emotional ups and downs if we don’t understand weight loss vs. fat loss.

You know the scene. You’ve had a “perfect” week of workouts and clean eating. You feel amazing. You can even see that you look better in the mirror – leaner, tighter, smoother. Then, you step on the scale, and – poof – your confidence (and your good day) evaporates as you see that you’ve actually gained one pound.

What gives?

When I first start working with clients, one of my first goals is to establish a healthy, self-caring, logical method for tracking progress. And a major part of that is understanding the difference between weight and body composition. In other words, weight loss vs. fat loss.

If you develop a solid understanding of how weight and body fat percentage work and how to measure them effectively yourself, you truly liberate yourself from the emotional drama of the scale.

I don’t just know this as a personal trainer and nutrition coach focused on women’s health – I also know this from my personal experience of losing a significant amount of weight and keeping it off (then having a baby, and having to lose it and keep it off again).

In this blog post, I’m going to share with you…

  • What body composition (body fat percentage) really is and how to measure it 
  • What 6 facts about weight you must understand to have a healthy relationship with it

Let’s go!

What is Body Composition?

Body composition includes weight, but it transcends weight. It’s simply body fat percentage – how much of your bodyweight is made up of fat, vs. how much of your body weight is composed of muscle, bone, water, and other “lean” tissue. 

Body fat percentage is an incredibly important metric of health, and I’ve written about it before in another one of my all-time most popular blog posts, “Female Bodyfat Percentage: What’s Right for You.”

It’s hard to know your body composition without knowing your weight, but body composition is like x-ray vision into what your weight actually means. Two women of the same height could weigh 150 pounds, but if one woman is 24% body fat and the other woman is 28% body fat, that means that one woman is a lot leaner than the other one, even if they’re the same weight.

This helps you understand weight loss vs. fat loss – I have clients who lose a certain amount of weight, but far more fat than weight because they’re gaining muscle at the same time.

You can measure your body fat percentage at home by using a combination of weight and measurements. I’ll dive into that in just a minute – keep reading!

6 Facts About Weight You Must Know

Understanding these six concepts will be incredibly freeing – you will stop stressing over the scale and its many tiny (or not-so-tiny) fluctuations.

Weight is a lagging indicator

This is a nuanced topic that hardly anyone understands about weight, but once it clicks, you are tremendously empowered to stop stressing.

Weight is a lagging indicator. When you weigh yourself, you are not necessarily seeing the product of the last day, or even few days, or even the previous week – you are seeing an average of the previous 7-21 days. What you see on the scale is delayed. It’s like being in a large stadium, where you see someone clap on the stage, but you don’t hear it until a second or two later.

This is a key fact because it can help to prevent reactivity to weighing yourself. Let’s say you see a number on the scale that surprises you – either it’s better or worse than you thought it would be that particular day. Often, this prompts you to make a judgment about whether or not something you did in the last 1-2 days had an effect on your weight, when really, what you did in the last 1-2 days may not be showing up yet. The problem is that you might change your behavior based on the information, in a way that’s not helpful to you (either becoming more restrictive, or acting out with overeating).

This is partly because you tend to have the best recall of what you’ve been doing for the last 48 hours or so. The previous 7-21 days has already receded into foggy memory. But the reality is that your weight is a product of averages over time. If you’ve been averaging a 20% calorie deficit for a few weeks, your body will start to sort things out accordingly. But if you’ve been in a 20% calorie deficit for a few days, your body may not have gotten the signal yet.

The truth is, if you could just collect the information, keep doing what you’re doing, and then compare numbers month-to-month, you would have a very accurate idea of what is happening with your weight. Don’t overreact based on one day’s weight. You have to give things time to catch up with you.

Weight and bloating are not the same thing

Bloating is a digestive issue, not a body composition issue.

Without going too far down this rabbit hole, bloating often feels like weight gain because it often triggers the same sensation of your pants getting tighter. But you’ll notice that the distinct sensation of bloat often tends to happen as the day goes on. We often don’t wake up feeling bloated – it accumulates throughout the day.

To some degree, this is normal for everyone, especially if we don’t call it “bloating” and think of it instead as simply having more food in the digestive system. When we eat, the food has to go somewhere – it doesn’t “burn off” instantly. It’s normal for your belly to poke out a little more and to feel “less lean” as the day goes on. We also tend to have more bloating during certain times of the month when our digestive systems slow down, like during ovulation and PMS.

Of course, there is also bloating that is indicative of a digestive issue – this is can be something like SIBO (small intestinal bacterial overgrowth) that requires treatment. But keep in mind that pathological bloating issues can also occur because of under-eating and restricting – our bodies need a wide variety of plant starches and fiber to maintain a healthy gut biome. Unnecessarily cutting out food groups can hurt your gut health instead of help it.

If you feel that you deal with serious bloating issues (i.e., you look pregnant after you eat), a trip to an RD is in order. Weight loss isn’t what will help – very lean people can deal with severe digestive issues.

A lot of your weight is water, and it can change quickly

Unrelated to bloating, have you ever dined out, and been five (shocking) pounds heavier the next day?

The good news is that this is not body fat. It’s water.

In the next point, I’ll be diving into what factors can affect water weight (and which are more or less under your direct control), but first I want to talk about how quickly water weight can move up and down. Body fluid makes up the majority of our body composition, and our bodies are good at quickly storing it and offloading it as needed.

The key takeaway here is that our bodies are much better at loading and dropping water than it is at gaining muscle, burning fat, or storing fat.

Water may be a huge part of our body composition, but it’s not body tissue. This means that it’s not a lagging indicator – it can jump up and down shockingly fast. On the other hand, changing body tissue is mind-numbingly slow – it takes weeks for your body to make significant changes to solid tissue.

Your water weight is affected by things you might not realize

It moves quickly, and it can be affected by…

  • Dining out (the sodium)
  • Alcohol intake
  • Travel (especially air)
  • Menstrual cycle (ovulation and menstruation)
  • Heavy workout or hard run (slight inflammation/recovery)
  • Illness/medication
  • Stress (cortisol)
  • Changes in carbohydrate intake (lower carb diets tend to cause loss of water weight)

Especially for women, weight can jump up for seemingly no reason at all, and this is especially frustrating after a “perfect” week of exercise and nutrition. But in the background, you might be ovulating (which many women are not aware of) or recovering from your workouts.

You’ll notice that the opposite might also be true – if you go on vacation and take a week off of workouts, you might come back lighter, because your body is so completely recovered and inflammation is low. This doesn’t mean, however, that you shouldn’t work out as part of your weight loss journey. That’s the problem with scale reactivity – you can misinterpret what you’re seeing and make changes that your body doesn’t want or need.

A Combination of Weight and Measurements is the Best

Adding in measurements can help to contextualize what number you’re seeing on the scale. For some people with a “weight loss goal,” the truth is that they have a fat loss goal. It is possible to lose a lot of fat without losing a lot of weight, particularly for people who start strength training seriously. For some people, they might not lose any weight at all, but their body fat percentage drops as they gain muscle and lose fat at the same pace. This is called “body recomposition.”

For people who will undergo this kind of body recomposition without significant weight loss, they would probably give up in frustration if they were only measuring weight – and they wouldn’t see the amazing results. This is why measurements are so important – they can demonstrate where and how fat loss is happening as we get stronger and leaner, and they can be reassuring if the scale is hardly moving at all.

For home measurement of body fat percentage, I recommend using a combination of weight and measurements at three key spots:

  • Neck
  • Smallest part of waist 
  • Widest part of hips/butt

(If you’re a man, these measurements would be neck and navel instead). 

Combine these measurements with weight and height in a calculator like this one, and you’ll get a fairly accurate idea of your body composition. This number isn’t only important for calculating fat loss – it’s also extremely helpful for knowing your lean body mass so that you can estimate your protein intake needs. For active people, it’s a great goal to match your protein intake (in grams) with your lean body mass weight (in pounds, not kilograms).

In other words, if your lean body mass is 110 pounds, it’s a good goal to aim for 110 grams of protein per day.

I like using this method so much more than something like a smart scale, handheld device, or even the InBody scans at some gyms. Even calipers can be extremely prone to user error. Weight and measurements are the easiest, most accurate, and least expensive way to assess progress, and if someone wants to take it to the next level, I would recommend getting a DEXA scan (which is more thorough and also measures bone density, which is a key fact for women).

For most of my clients, I recommend doing measurements every 2-4 weeks. For weight, I recommend one of the following choices (depending on the client’s preference):

  • Weighing frequently (i.e., daily or almost daily) to capture lots of snapshots and data
  • Weighing twice a week on a flexible schedule (i.e., Tuesdays and Fridays)
  • Weighing “once a month” but for 3-4 days in a row to get an average (then waiting 27 days to weigh yourself again)

All of these weighing schedules help to prevent the phenomenon of catching yourself on a very high or very low day. What we want is the average, and more data points help with this.

It’s okay to not use the scale

Finally, it’s okay not to use the scale at all! In fact, for some people, over-focusing on the scale can distract from process.

Your weight loss process is the tapestry of behaviors that you do to encourage healthy weight loss – exercising, hydrating better, making nutrition changes, etc. Process is typically within your direct control (within reason).

Weight loss is a product, or outcome, of this process. Unfortunately, when we focus too much on end results, we can become distracted from actually doing the things that would help us get there.

We cannot control the outcome, but we can control many of the small factors that help us to feel and perform better every day. It’s incredibly important to know yourself and your tendencies, and understand how easily you get discouraged and what will help you stay motivated.

For some people, buffering the disappointment of an unwanted scale reading is an easy task. For others, it’s enough to distort all joy and positivity around lifestyle change. If you find that weighing yourself typically “ruins your day” or otherwise radically changes your process, it’s probably not a good metric for you.

As one client said to me, “It would motivate me if the number was actually going down.” So if it’s not going down… what then? What are you going to rely on to motivate you?

There are many other ways to know that you’re getting healthier, like:

  • Workouts getting easier (or getting harder and you’re able to keep up with them)
  • Sleeping better at night
  • Feeling less hungry and more satisfied from your meals
  • Feeling more empowered around your healthy food choices
  • Blood work improving
  • Clothes fitting better

Scales are so easy and accessible for us to use now, I think it’s easy to forget that we didn’t always have them. It’s not necessary to know your weight to know if you are healthy or not, exercising or not, or eating mindfully or not. More importantly, scales don’t tell anyone if they are worthy or not.

Focus more on process and less on outcome, and even if you do weigh yourself somewhat frequently (as many of my clients do), you’ll be a lot happier!

Rachel Trotta

I am a Certified Personal Trainer, Fitness Nutrition Specialist, Physique and Bodybuilding Specialist, and Women's Fitness Specialist. I live in New Jersey in the NYC metro area, and I coach clients online all over the world. As a trainer and health writer, my mission is to make healthy living sustainable for the average person. I’m also a wife, mom, nature lover, runner, avid cook, weightlifting aficionado, history nerd, travel addict, and obsessive podcast listener. Get in touch!

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