Wondering if you should focus on weight loss vs fat loss? Or fat loss vs weight loss? In this post we will discuss the latest scientific findings behind why focusing on EITHER may be unhealthy and what you SHOULD be shifting your attention towards instead!

Body Composition Overview

Our bodies are composed of multiple components – not just muscle and fat.  There are several models that look at how our bodies are made up. On one hand we have the basic 2 compartment model, where the body is summarized into two components, fat and fat free mass, otherwise known as lean body mass. 

And on the other hand we understand that the body is much more complex than just 2 categories. This has lead to the creation of multi-compartment models. These more complex models that break down the body into many more components including everything from different elements, fluids, tissues and bone. 

When we refer to fat free mass (FFM) or lean body lass (LBM) when discussing the difference between fat loss vs weight loss know that FFM/LBM includes:

• Organs
• Fluids
• Bones
• Muscle

This FFM is what is trying to be maintained (or even increased if your goals include building bone density and/or muscle) for those who are attempting to focus on fat loss. 

The 3 Different Types Of Fat

When we discuss fat in terms of weight loss VS fat loss, it’s important to note that we have three types of fat that each function differently:  

• Brown Adipose Tissue (BAT) – functions as thermogenesis (what keeps our body temperature steady), known as the ‘good fat’, functions in energy expenditure to produce body heat and has more mitochondria (little energy burning centers) than white fat
• White Fat – provides energy while we’re fasting (sleeping or even ‘dieting’), energy storage (just because this isn’t known as “good” fat doesn’t mean it’s “bad”! It’s normal and provides essential functions)
• Beige/Brite Fat – this is when brown adipose tissue is in white fat. It is thought to have similar function to brown adipose tissue, thought to be able to switch between energy expenditure and energy storage

These differentiating fats are an emerging area of science, and we are learning more about how different types of fat can be beneficial and detrimental to our health. At this time (to my knowledge) body composition measures reflecting the proportion of types of fat are not readily available and/or used in dietetics practice, though a fMRI protocol has been tested in very small sample (n=5) to determine this proportion.

How Body Composition (Overall Weight VS Fat) Is Measured

There are several ways to measure our body composition in order to discuss and determine weight loss VS fat loss, including: 

Bioelectrical Impedance Analysis (BIA)

BIA functions by sending a small intensity electric shock through your system. With this electric shock, our FFM and fat mass each resist this electric current differently. The number given can tell us how much FFM and fat mass we have, based on the amount of current that has passed through us.

The more resistance, the more fat mass. Some advantages to this measure is that it is portable, noninvasive, and inexpensive. Unfortunately like any measure, it has some variability. Being dehydrated, having caffeine or exercising prior to measuring can skew the results. 

Here’s an example of what BIA can tell us: 

Underwater Weighing (aka Hydrodensitometry)

Underwater weighing is considered the gold standard in measuring body composition. The way it works is to first weigh someone on a scale, and then to place someone in a tank of water with a specific amount and see how much water the body displaces.

All air must be ‘pushed out’ of your lungs, and air in the GI tract and lungs must be corrected for. Based on Archimedes’s principle, the volume of the water displaced is equal to the volume of the object. Body density is then determined from this displaced water, and then percent body fat can be determined from equations that are specific to gender, age, and population.

Some of the disadvantages of this measure is that it is big and bulky, those being measured must be trained on how to submerge properly, it is not practical for measuring multiple individuals, and requires a trained technician. 

Dual-energy X-ray absorptiometry (DXA)

A DXA machine sends low dose x-rays through the body to determine your fat mass, LBM, and your bone density. This has always reminded me of a ‘copier machine’ for your body. A participant must remain completely still through the scan (7-15 minutes).

This is also considered a gold standard measure of body composition, and is non-invasive with very little radiation exposure. It can give instant results, though it is an expensive machine that requires a trained technician.

Remaining still throughout the measurement may be difficult to do, as well as pregnant women, those who weigh more than 450 lbs, and those with spinal deformities may not be measured using this method.

Here’s an example of the amount of detail a DXA scan can give us on the same individual’s body composition:

You can see that there are differences in the two measures, and that BIA mentioned above overestimated the amount of lean mass, though was very similar among the amount of fat mass. 

Air Displacement Plethysmography (BodPod)

A BodPod is similar to underwater weighing, though uses the displacement of air rather than water to measure body composition. Participants are placed in a chamber and the air they displaced is used to calculate their composition based on ethnicity and gender.

Prior to a BodPod measurement, one must fast for 4 hours, empty their bladder and bowels, not exercise for at least 4 hours, and wear a tight fitting swimsuit and cap. This is a relatively non-invasive measure, and limited effort is placed on the participant (much different than underwater weighing).

This test also requires a skilled technician, expensive equipment, and may make some participants claustrophobic from being in the chamber. 

Skinfolds

Skinfolds is a method using a device called a caliper to make measurements at multiple parts of the body to determine one’s body fat. Similar to the other measures, it does require a skilled technician, and the equations that the measurements are placed into, assume that 50% of fat is subcutaneous, or under the skin.

It is relatively noninvasive and cheap, though there is some variability among technicians who may measure differently.

Overall, the amount of effort placed into measuring someone’s body composition takes time, training, and can still be variable (much like our day to day weights!) based on what we eat, drink, and our exercise regimen.

Why A Single Measurements Is Inaccurate

One measure, such as the scale that tells us our weight – will never be an accurate predictor of health. By saying that people are ‘overweight’ or *bese with a simple math equation (aka BMI), it doesn’t account for where that mass is coming from (or even what kind of fat they have)!

This can be applicable to so many people who may have additional brown fat, muscle, or bone density. Using BMI to accurately describe our health is like taking one line of our resume to determine whether or not we are the right person for the job.

Both lack context. Another sad *bonus*  – BMI has even been denounced as an accurate measure of *besity in adults by improperly associating BMI to an unhealthy body fat percentage, which can contribute to metabolic syndrome and other risk factors for chronic disease. 

Yet another reason that you are more than a number and we are each our own best healthcare advocates. 

So, What is the Difference between Weight Loss and Fat Loss?

Now that we know what our body composition is composed of, you can see the difference between weight and fat loss. Weight loss does not distinguish whether or not we lose fat mass or lean body mass. 

This is one of many reasons why using the scale (or any one measure!) to determine our health is not a good practice. The scale doesn’t reflect the difference between types of mass that we can lose.

So, those fad diets you read about in magazines in the grocery store check out saying that you’re losing 10 pounds in a week? You’re losing water weight and some muscle mass, part of our lean mass, which if we want to lose any weight, is not the weight we want to lose!

Is Focusing On Weight Loss Unhealthy?

Focusing on weight loss in your health journey shouldn’t be the main goal on your wellness journey. We’ve discussed how weight/BMI aren’t accurate predictors of health, and we know that health behaviors such as eating 5 servings of fruits and vegetables, regular exercise, moderate alcohol consumption, and no smoking were better predictors of health than weight alone.

And when we continually weight cycle aka ‘yo-yo’ diet, we may be placing our bodies at more risk for chronic disease, high blood pressure, lessening bone density, and Relative Energy Deficiency in Sport (RED-S).

There is growing research to support a set weight (see my post on set weight), a weight that our bodies want to be at to function optimally. Weight is not a food + exercise equation that our society (& the diet, ‘wellness,’ and ‘fitness’ industries) wants us to believe is in our complete control.

Our bodies are complicated, smart machines that involve more than just the hormones we are familiar with that give us our period each month. These hormones help us maintain all of our body processes, wake us up and put us to sleep, and also help to tell us when we’re hungry. 

Does Fat Loss Actually Mean ‘Healthier?’

Fat loss doesn’t necessarily mean healthier. When we discussed our body composition and the different types of fat we all have, losing our brown fat isn’t something we want to do. It helps keep us at our ideal body temperature for metabolic processes.

Honoring our bodies through exercise we enjoy and gentle nutrition, we know that our health benefits, no matter our weight.

And when we try to alter our body’s set weight to lose weight, we alter our biology and our body’s response, which can lead to even more weight gain (the opposite of what we’ve intended).

Take the famous Biggest Loser contestants for example, with the weight they lost, they will have to consistently increase their exercise to maintain their weight loss. And at a 6 year follow-up, they regained weight, while also slowing their metabolism, making it even harder for their bodies to ‘lose’ it the next time. 

Again, we know that our bodies can become healthier through health promoting behaviors regardless of what happens to our weight!

I’d highly recommend checking out my blog post on Health At Every Size (HAES) for more on this topic of being healthy regardless of weight loss!

How To “Manage” Your Weight

Though ‘diet’ is in my title as a registered dietitian, a diet isn’t something that will help you. With the word diet, it’s important to think of your ‘diet’ as in your overall relationship with food, a dietary pattern, versus a plan that you follow to lose weight.

Technically, we all have diets! It’s simple the way you eat. This can change throughout time and doesn’t have to check a box or have a label. It just IS.

So, back to managing your weight…. it is an unsexy answer but you don’t need to manage your weight. Your body already does that for you with its set point. Essentially, to sum up the set weight theory, your body has an intrinsic thermostat that will work to keep you at your optimal weight to foster overall health & wellness… but only if you  listen to your body! This is what I teach in The SociEATy.

When we try to “manage our weight” with long-term diets, in the end it doesn’t work. A study showed that this act of “weight management” had a success rate as little as 6%, over a 15 year follow-up period.

When we mess with our body’s intrinsic management of our weight, we may be setting our bodies up to regain + gain back any weight we do lose from these set points (even so much as 145% of our original fat mass!). 

When we try to mess with that weight by controlling our intake or over exercising – our hormones work their hardest to protect us. As we change, our bodies change. When we grow as individuals (physically and as beings) our bodies acclimate to set points and settling points.

Our bodies adapt to meet the needs of each season we enter – such as overcoming an illness, growing a baby, or building up muscle to prepare for a marathon. These settling points help us maintain balance in our lives. 

Adopting A Weight Neutral Approach

Now, with all of this being said, is it BAD to lose weight? My answer is absolutely not. I DO think it can be more harmful than beneficial, based on the scientific studies mentioned throughout this post, to try to intentionally lose weight.

It’s possible that some bodies may be ABOVE their set point weight and when one starts to listen to their body through intuitive eating that weight loss might happen and might be healthy.

There are other people who may be below their set point weight and weight gain may happen in order to be healthy. Others may simply maintain their current weight if they are at a weight at which their bodies like and feel good at. None of these outcomes are bad and they ALL happen.

I know that this is SO different from what we’ve thought about our weights for so long and can be really tough to get your head wrapped around. Definitely checkout the books Health At Every Size and Body Respect to learn more about this weight neutral approach to health!

Again, to reiterate: as we change, our bodies change. 

We don’t have the body we did in high school because we’re not in high school any more. 

We don’t have the body we did before we were pregnant because prior we hadn’t grown a human and continued to make food for and feed and care for another with our own body. 

If our bodies were as simple as an energy in + energy out equation, wouldn’t we all look the same? No. Because even if we all ate the same, we wouldn’t look the same.

I hope this post was super helpful and eye opening, encouraging you to shift your “goals” away from asking the question “Which is better? Weight loss VS fat loss” to “What health promoting behaviors can I incorporate?”

Be  sure to leave a comment with your thoughts on the topic of weight neutrality! I can’t wait to open up this convo!

XOXO

-Colleen

This blog post was reviewed by Colleen Christensen, RD and researched & written with the help of Amy Sharn, MS, RDN.