The Truth About Weight Loss vs. Fat Loss

Writtenby Dr. Charlie Seltzer Tagged as Weight Loss

August 29, 2018

Has this ever happened to you? You’re trying to lose weight and get on the scale after following your plan to the T for a week, only to find it is inexplicably up 2 pounds? Or have you ever fallen off the wagon for several days only to find the scale shows you lost weight? If so, you’re not alone. These fluctuations are very common and can either send you into an unnecessary tailspin or give you a false sense of security. This guide to fat loss vs. weight loss will help you understand and be at peace with the scale and its fickle nature.

Muscle vs. Fat: Explained

When people say they want to lose weight, what they really mean is that they want to lose fat. Most of the time, “toning” (which really means building some muscle and losing fat) is also high on the priority list. If you have never lifted weights before, your body composition can change significantly for the better, even though the scale seems to be on another planet.

What is body composition you say? Body composition is a way of describing what your body is made of when it comes to fat, muscle and all of the in between. It is a much more useful and effective way to analyze weight as opposed to the traditional BMI measurement.

First off, muscle is denser than fat, meaning if you replace one pound of fat with one pound of muscle, you will take up less space, or be “smaller.” So, you could see changes in clothes and in the mirror but not on the scale. Yet, there is definitely fat loss.

One of the first adaptations the body undergoes in response to starting a strength training program is to hold more sugar in its muscles. Every sugar molecule binds to 3 molecules of water, which can cause a significant rise in the scale with the same, or lower, body fat. In addition, the inflammation that often occurs with strength training can cause the scale to go up even more.

However, in neither of the above scenarios does fat go up, even though the scale does.

How Do I Lose Body Fat Quickly?

In order to lose fat, you MUST consume fewer calories than you burn. THIS IS THE ONLY WAY TO LOSE FAT! If you maintain a calorie deficit and do not train with weights, a significant amount of the weight you use will be muscle, which is not desirable. If you keep the same calorie deficit and resistance train properly, you can ensure the weight you lose is fat, and you may even be able to build a little bit of muscle.


How to Eat for Fat Loss

Like I said above, in order to lose fat, you must eat less than you burn. This rule holds true no matter what plan you’re following – keto, Paleo, low carb, low fat, high protein, high carb, whatever it is. Your best shot at maintaining a calorie deficit is to first know what your daily calorie requirements are.

There are equations you can use as well as metabolic testing machines. The three ways you can calculate your metabolic rate are the Mifflin-St Jeor Equation, Revised Harris-Benedict Equation: or the Katch-McArdle Formula. The NIH Body Weight Planner is one of the most accurate calculators when it comes to computing your estimated calorie intake.

You can also record your food for a two-week period without changing the way you’re currently eating (or exercising- this is just data collection) and follow your average weight for those two weeks. If the scale stays the same, your maintenance calorie number is what your average daily calorie intake is. If the scale goes down, your maintenance calorie number is more than what your average calories were over the last two weeks (If this happens, don’t change anything and see how long the weight loss continues). The scale goes up, your number is lower.

Once you have your maintenance calorie requirement, decrease by ~5-10% (If you were eating 2000 calories per day, you would go to 1800.) Here is where a lot of people get it wrong. Do not try to overhaul your life overnight. It will go very very poorly, trust me.

You should be shooting to change as little as possible in order to get the scale moving. The more you try to change, the more likely it is to backfire. Also, the more you deviate from your natural tendencies, the less likely you are to succeed.

Losing weight is very challenging for anyone. However, if you add in poor sleep, fatigue, stress, anxiety, depression, and pain it becomes even harder. In order to maximize the likelihood of success, it is important to look at the big picture, not just what a person is eating and if or how he or she is exercising.

In my practice, we spend a significant part of our visits (especially in the beginning) addressing the “life-is-getting-in-the-way” barriers to achieving fat loss. By making our patients feel as good as they can, they can concentrate more on doing what needs to be done to lose fat.

So, work with your tendencies and food likes rather than against them. It will be invaluable in the long run.


How to Exercise for Fat Loss

It is pretty clear from the extensive research we have that exercise will not help with weight loss unless you’re also controlling for your food. Even this, its impact is minor compared to dietary changes.

That said, exercise can help speed up the process, especially if that exercise is high intensity training and/or resistance training. When you train with weights or do high intensity bouts of cardio (like sprinting), you use calories to fuel the activity, which then need to be replaced when the exercise is completed.

The more energy you expend during the activity, the more energy needs to be replaced. This energy deficit is corrected by the oxidation (breakdown) of fat molecules, which results in loss of body fat. This process is called excess post exercise oxygen consumption (EPOC), or the “afterburn effect.”

In addition, weight training stimulates new muscle growth, which requires the addition of new amino acids –the building blocks of protein) to the muscle. This process also requires energy which comes from the breakdown of fat. These effects may be minor in isolation, but they can be significant over time and, with patience, can result in drastic aesthetic changes.

It is also worthwhile to mention that muscle uses more energy at rest than fat does. So, by carrying more muscle, your body burns more calories at rest. However, this effect is not as significant as was previously thought, but is still one more reason to train with weights.


How Do I Burn Fat and Not Muscle?

How do you lose fat at the most optimal rate while sparing the muscle you currently have.

In order to minimize the likelihood of muscle loss while losing fat, it is important to engage in regular resistance training. If you don’t, the likelihood of losing muscle is very high. It is equally important to keep the rate of weight (fat) loss appropriate, which is about 0.5-1% of body weight in fat per week at a maximum.

For example, on a 200-pound person, that works out to 1-2 pounds per week. For a 150-pound person, it is 0.75-1 pound per week. The lower your calories are, the more likely you are to lose muscle mass and “go off the rails,” risking overeating significantly from the severe calorie restriction.


How Do I Measure Whether I’m Losing Weight or Losing Fat?

There are many ways to measure body composition. Below are the most common methods of measuring body composition to understand your fat loss progress.

  • DEXA Scan
  • Calipers
  • Body Circumference Measurements

Following the values over time is helpful to know whether your plan is working. DEXA scanning is highly accurate but is expensive and requires a trip to an imaging center. Calipers are cheap, and in a skilled person’s hands, are very accurate. I actually tend to stay away from using measurements like calipers, as I have found the amount of “user error” is huge.

Another, less scientific but equally valuable way to determine whether the scale drop is fat or muscle is this: If your clothes are getting looser and your strength in the gym is stable or improved, it is a safe bet that you are not losing muscle.

It is important to remember that muscle growth is a much slower process than fat loss, so after the initial adaptations to beginning a resistance training program (which can be days-weeks or possibly even months), the scale should go down if you’re losing fat. If it is not, but your shape and how your clothes fit are changing, it may be useful to follow objective measurements, like a DEXA scan or calipers.


Ready to focus on fat loss but unsure where to start?

If this seems like a lot of information, its because it is a lot of information!

Fat loss in theory is simple: eat less than you burn and exercise. Strength training is the most effective form of exercise for burning fat and growing muscle, so that’s why I craft a customized workout plan for all of my clients as part of their weight loss prescription.

Where it gets complicated is trying to execute that simple idea in the context of your life and the real world, along with its commitments, uncertainties, stress and lack of time.

But it doesn’t have to be.

I have a patient who works more than anyone I have ever met. He literally barely has time to sleep. As much as we would both like him to prepare and eat his own food, it is just not currently feasible. Out of necessity, most of his meals are prepacked, fast food, etc. Even though this is not ideal, he is still averaging about a pound of weight loss per week (eating between 2100 and 2400 calories per day with a minimum of 120 grams of protein). He has lost 15 pounds over the past 3 months. He is an example of how controlling your intake, regardless of where the food comes from, will result in predictable weight loss.

With a proper weight loss program that includes both nutrition and exercise components (as well as medication and supplements when appropriate), you can successfully navigate the ebbs and flows of losing fat, making positive changes in your health, and getting that body you always dreamed of!

About The Author


As the only physician in the country to be board-certified in Obesity Medicine and certified by the American College of Sports Medicine as a Clinical Exercise Specialist, Dr. Seltzer has a proven track record of helping people transform their lives for good.

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