What Happens to Your Body After Major Weight Loss?

Thu 29th May 2025

Losing a considerable amount of weight can be an exciting process. And there are many benefits to experience once you’ve shed those kilos.  Your mood, brain function, and sleep will improve, you’ll have more energy, and your risk of developing chronic diseases and cancers will be lower—and so much more. But after major weight loss, you might also find yourself with problematic excess skin. Fortunately, though, surgery can remedy this problem.

This article explains some of the changes your body will experience and the surgical options available to address problems with excess skin.

WHAT WE’LL COVER:

• The weight loss journey: Understanding weight loss versus fat loss
• Bariatric surgeries: weight loss estimates
• Physical and mental changes after major weight loss
• Addressing excess skin: surgical options
• Choosing the right plastic surgeon for your procedures

Before we look at the changes to expect after losing weight, let’s quickly cover what happens to your body while losing weight.

Many of us use the terms ‘weight loss’ and ‘fat loss’ interchangeably — after all, they both make us lighter. However, the two terms mean different things. ‘Weight loss’ includes any stored proteins, carbs, water and fat in our body, while ‘fat loss’ is purely the loss of fat and occurs at a slower rate.

Stage I – Dramatic weight loss

When we first start to lose weight over the first four to six weeks, we experience rapid weight loss. This is mainly due to water loss and small amounts of protein, fat, muscle and glycogen. The scales show that we have lost weight during this time, and our clothes fit more loosely. Things feel like they are tracking nicely. But technically speaking, we still aren’t losing a lot of fat. To lose fat, we must first deplete our glycogen supplies.

Glycogen is the name given to sugar your body stashes away, mainly in your liver and muscles. You can think of it as a backup store of energy. Once you have depleted your glycogen stores, you can start burning fat. 

Stage II – Fat loss

As you enter your second weight loss stage, everything slows down. Your weight loss won’t be as dramatic, as you are not losing all that water, and it may even plateau. Even though the exhilaration of watching dramatic changes on the scales has gone, the good news is that you are usually only burning fat now.

It’s important to note that weight loss happens at different rates for everyone. Various factors determine the speed of your weight loss, such as your age, sex, diet, how much you are exercising and your starting weight. (If you start at a higher weight, losing the first few kilos is easier.)

Bariatric surgery and weight loss

If you’re considering losing weight through bariatric surgery, such as gastric sleeve, gastric bypass or lap band surgery, your weight loss will likely be substantial — although amounts vary, depending on your procedure.

Here are the three most common types of bariatric surgeries in Australia and the estimated excess body weight you can expect to lose:

• Gastric band surgery: 30 to 40% loss of excess body weight
• Gastric sleeve surgery: 50 to 60% loss of excess body weight
• Gastric bypass surgery: 60 to 70% loss of excess body weight

Physical & mental changes after major weight loss

Better sleep

You may sleep better at night once you’ve lost significant weight. Many overweight people suffer from breathing problems, such as sleep apnoea, at night. Once your excess weight has gone, your breathing troubles will abate, and you may find it easier to sleep through the night and be more energised throughout the day.

Improved mood

Losing weight won’t just change the way you look. Individuals who have experienced significant weight loss report less tension, anger, depression and fatigue. Keeping a healthy weight also lowers your risk for depression and anxiety.

Improved brain function

Studies indicate that obese individuals have trouble with thinking, memory and overall brain function. Certain parts of the brain may also become more active after weight loss.

Better sex life

Obese people often report a low interest in sex, while overweight men may struggle with erectile dysfunction. Fortunately, though, once people lose weight, the quality of their sex life often improves.

Reduced risks of major diseases

A vital benefit of weight loss is reduced risk of many serious diseases and health problems such as osteoarthritis, stroke, heart disease and diabetes.

Increased energy

An overweight body demands a lot of energy to function. Therefore, your energy levels will dramatically increase if you lose significant weight. Additionally, your body will function far better if you’ve switched to eating more nutritious foods.

Excess skin

An unwelcome downside of significant weight loss is excess skin. And unfortunately, this skin won’t snap back into place on its own. The only solution is surgery. Below, we explain more about skin laxity and the surgical options available.

Skin Changes: Elasticity, Sagging and Other Effects

If you’ve put in the hard yards to successfully lose weight, either on your own or through bariatric surgery, it would seem only fair that your hard work ends there. However, many individuals discover a new problem—loose, sagging skin—which can cause significant physical and emotional issues.

To understand why our skin sags, we need to understand the composition (and function) of our skin. Our skin is the largest organ in the body, designed to protect the body from the environment. The deepest layer of the skin consists of the proteins collagen and elastin. Collagen gives your skin its structure, making it firm and strong. Elastin gives it the elasticity to help your skin stay tight.

If an individual puts on a significant amount of weight, the skin expands to make room for this increased growth. Pregnancy is a good example of such activity. However, with pregnancy, the skin expands over several months and then slowly contracts a few months after childbirth. In contrast, if an individual puts on weight and stays that way for some time, the collagen and elastin fibres become damaged. Consequently, the skin loses its ability to retract.

Furthermore, when stretch marks develop with rapid weight gain, often seen with pregnancy, then that segment of skin is now damaged with increased surface area and reduced elasticity.

Whatever the cause of the weight loss, in the end, the body gets smaller, but the skin cannot ‘shrink wrap’ around the smaller body and starts to hang. Everyone is affected differently, but ultimately, this is the process.

A simple analogy is to think of the skin like your clothes. Therefore, if an individual loses a lot of weight and the body gets smaller, the skin starts to hang like clothes designed for a much larger body. The more weight you lose, the more obvious your sagging skin becomes.

There are various contributing factors to loose skin following weight loss:

• Genetics: Your genes may affect how your skin responds to weight gain and loss.
• Chronic sun exposure: Sun exposure reduces the skin’s collagen and elastin production, contributing to loose skin.
• Age: Younger skin has more collagen, while older skin has less and tends to be looser after weight loss.
• Amount of weight loss: Losing a substantial amount of body weight (and losing it rapidly) typically results in more loose skin than moderate weight loss.
• Length of time overweight: Typically, if someone has been overweight or obese for a longer time, the skin is looser due to collagen and elastin breakdown.
• Stretch marks: Skin with significant stretch marks is less able to shrink than skin without stretch marks. 

Physical Effects of Skin Laxity After Weight Loss

Excess skin can cause serious physical problems, such as fungal or bacterial infections, rashes, chafing, problems fitting into clothes and functional issues, such as being unable to exercise due to excess skin tissue impairing movement.

 Emotional & Psychological Effects of Skin Laxity After Weight Loss

Although the benefits of weight loss, or bariatric surgery, are significant, finding yourself encumbered with an abundance of loose skin can not only be extremely disappointing but also raise its own set of debilitating problems. For example, excess skin can cause:

• body image problems
• impaired mental and physical well-being
• self-consciousness
• withdraw from social activities
• anxiety and depression

All these problems, both emotional and physical, can leave an individual feeling just as depressed as when they were severely overweight.

Excess Skin Removal Surgical Options

Loose, excess skin after weight loss cannot be fixed by lifting weights or laser treatments. The only way to remedy this problem is through Body Contouring Surgery.

Body Contouring Surgery encompasses a range of surgical reconstructive procedures tailored to your body. They address the often significant functional and aesthetic concerns of loose, excess skin. Using a dress-making analogy, the surgeon must tailor your skin to fit your now smaller body. The areas of excess skin and the surgical pattern required for optimal tailoring dictate the subsequent scars.

Various Body Contouring surgical procedures are available, depending on an individual’s issues. Dr Dona has developed a system where he has grouped the key surgical procedures frequently required after dramatic weight loss. He calls these ‘The 7 ‘B’s of Body Contouring Surgery. They are:

• Brachioplasty (Arm Reduction): Removes excess skin from the upper arm.
• Breasts – Lifts, Reductions and Augmentations: The breast can be reshaped in various ways depending on the patient’s concerns.
• Bra Lipectomy (Upper Body Lift): Removes excess skin rolls and associated fat in the upper and middle part of the back and around the bra strap area.
• Belly – Abdominoplasty (Tummy Tuck): The abdominal wall can be reconstructed depending on the patient’s needs, addressing issues such as excess skin folds, muscle separation and damage, drooping (in the mons region) and possible abdominal wall hernias.
• Belt Lipectomy (Lower Body Lift, 360 Tummy Tuck): Removes rolls of excess skin and associated fat in the lower back, flanks, upper outer thighs and abdominal region. It also lifts the buttocks and pubic areas.
• Buttock Surgery: Removes excess skin from the lower back, lifting and tightening the buttocks.
• Below the Waistline Surgery – Genital And Thigh Surgery:

As extreme weight loss affects every part of the body, you’ll likely want more than one procedure. Fortunately, two or more procedures can be combined in one surgery, saving you time and considerable expense. If you’d like more procedures done, we suggest you undergo surgeries over a period of time, starting with the areas that concern you the most. Keep in mind that the minimum time between each surgery is three months.

Choosing the Right Surgeon for Body Contouring Surgery

If you’re concerned about loose skin after weight loss and are considering plastic surgery, it’s vital you choose a qualified and experienced plastic surgeon familiar with these issues to ensure you have the best chance of achieving optimal results. You want a surgeon with a proven track record in managing the many varied and often complex weight loss patients and numerous examples of their work that they can show you.

Plastic Surgeon Dr Eddy Dona has spent decades perfecting his craft, and a large part of his private practice is dedicated to looking after patients who have experienced massive weight loss. A meticulous practitioner, he consistently refines his surgical skills, maintaining a steadfast commitment to excellence in plastic surgery.

 

References

health direct: a guide to bariatric surgery

https://www.healthdirect.gov.au/guide-to-bariatric-surgery

Australian Journal of General Practice: Bariatric surgery

https://www1.racgp.org.au/ajgp/2025/april/bariatric-surgery