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What Happens When You Lose Weight? By a Bariatric Physician

Anthony Diaz
Published by Anthony Diaz | Bodybuilding Coach
Last updated: August 15, 2023

One of my clients recently shared how, after losing 107 pounds, she now seems unrecognizable to some of her relatives.

According to them, everything about her had changed, from her face to her body and her attitude.

As a fitness expert with 12 years of experience, I helped many of my clients go through those changes, so I decided to explain what actually happens when someone loses a few pounds.

I teamed up with a bariatric physician and compiled all of my data for this article.

Let’s dive in.

Quick Summary

  • When you lose weight, you will notice some changes in the body such as your waist, loose skin, and a change in body temperature.
  • Some benefits of losing weight include better sleep, enhanced sex life, better mood, and reduced health risks.
  • Fat-burning waste in the body is excreted as sweat, carbon dioxide, or urine.

What Changes Does the Body Go Through When You Lose Fat?

Holding two dumbbells in pink background

When you lose fat, your body undergoes several changes as you approach a healthy weight. The first thing people notice is clothes fitting differently.

Although the changes are usually most noticeable around the waist, for some people, the face also appears chiseled and slimmer than before [1].

You may also notice loose skin around the belly where there’s a significant amount of fat loss.

The changes are not just physical; scientists also assert that body temperature drops after dropping pounds [2].


Losing Weight Stages

Two person with different body type

Losing weight comprises two main stages in general; the rapid stage and the slow stage.

Let’s get into details about the two stages.

Rapid Weight Loss

The first stage of weight loss is somewhat radical. As we’ve mentioned, you start noticing changes in your physical appearance, your clothes don’t fit like they used to, and this period lasts for the first 4-6 weeks [3].

During this radical stage, most of the weight lost is water weight that is bound to glucose in your muscles in the form of glycogen (a form of stored glucose chains).

It also comes from some protein breakdown and fat, but to a lesser extent [4].

Related articleHow to Lose Weight Fast

Slow Weight Loss

In the second stage of weight loss, the process is slower. As the weight loss slows down, you may experience a plateau where there’s little to no change in weight despite your best efforts.

The silver lining is that most weight lost at the slow stage is pure body fat [4].

The lack of weight change can be accounted to the slowing metabolism as the body adapts to a new diet and fitness routine.

Another reason why it's slow is that folks deviate from overly restrictive diets. As such, you must choose a diet plan that fits your lifestyle in the long term.

Four Main Benefits

Women with good rest and good mood

As your body shrinks fat cells to produce energy, you also benefit from a plethora of benefits, including:

Better Sleep

Insomnia and other sleeping difficulties are much more common among obese people than in healthy people. One of the causes of such sleeping problems is sleep apnea. It affects overweight people more and can only be solved by losing weight [5].

A 2014 study by researchers from the University of Pennsylvania found that overweight people who lose at least 5% of their body weight sleep better and for longer after six months of shedding pounds [6].

Related articleCan You Lose Weight When You Sleep?

“You will find yourself sleeping better, feeling fresh, well-rested, and more alert. Better sleep also enhances your mood,”

- Dr. Harsha Gadre, PT, Orthopedic Physiotherapist, AquaCentric Therapy

Better Mood

A person with good mood

Overweight people suffer more from mental health conditions. They tend to have low self-esteem brought about by self-consciousness [7].

These problems bring about depression-like behavior but can easily be solved by dropping weight.

Taking in fewer calories and engaging in strength training to maintain muscle mass improves your physical well-being.

And as your pounds drop, your mental health improves in addition to your overall health.

The surprising fact about mood and sleep is that it goes both ways.

Research shows that high-spirited people drop more pounds than their gloomy counterparts [8].

Better Sex Life

The lack of sexual stamina, hormonal imbalance, and sexual dysfunction are often related to obesity.  Problems such as depression, self-consciousness, and mood swings contribute to poor sex life.

The solution is simple - dropping excess weight. And it has a science backing from a 2012 study that found losing weight led to improved sexual function in women [9].

Another study found that overweight men could cure erectile dysfunction issues by moving towards a healthier weight and making lifestyle changes [10].

Reduced Health Risks

Blood pressure rises with body weight. Being obese exposes you to numerous health risks such as heart diseases, diabetes, high blood pressure, stroke, osteoarthritis, and other conditions [11].

Where Does It Go?

Before and after fat loss

Our body has a complex process of breaking down fat into carbon dioxide and water.

Water is passed out through sweat, urine, and exhaled air, while carbon dioxide is disposed of primarily through breathing.

Exercising enhances the disposal of this carbon dioxide through breathing and sweating [12].


What’s the First Thing You Notice When You Start Losing Weight?

There is no clear-cut answer on what you’ll notice first when you start to lose weight. However, for most people, the first place they are most likely to see changes is their waist.

Will Losing Weight Make My Face Look Better?

Losing weight certainly affects face aesthetics.

According to studies, significant weight loss gives the appearance of an older but more attractive person, while mild weight loss gives the appearance of a younger but less attractive person [13].

Does Your Poop Change When Losing Weight?

Yes, your poop changes when losing weight. First, bowel movements are more frequent, and you might be constipated.

And if you’re on a low-carb diet, you might produce runny poops.

Is the Weight Loss Journey Worth It?

Avoiding your favorite meals and exercising regularly can be daunting at first, especially in the second stage, where there seems to be no change. But as we’ve seen, the benefits far outweigh the cost.

Now, as a remedy for the slow second stage, I always advise my clients to opt for high-quality fat burners for women or fat burners for men that we tried and tested ourselves both for effectiveness and safety.

Most of my clients who have used these products report positive changes. So make sure to check them out to see what they can do for you.


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