Armpit fat — that soft bulge between your upper arm, breast, and chest — is something you probably notice more when you wear bras, tank tops, fitted shirts, or sleeveless dresses. People call it all sorts of names: underarm fat, side breast fat, back armpit fat, arm fat. Whatever you call it, it’s pretty common.
Having a chubby armpit doesn’t mean you’re overweight. In fact, genetics, how your body stores fat, breast tissue, loose skin, hormones, or even the kind of clothes you wear can all affect how your armpit area looks.
But here’s the thing — not every bulge under your arm is actually fat. Sometimes, what looks like fat is really breast tissue, loose skin, or some other kind of tissue.
So figuring out what’s causing it helps you know how to deal with it.
What’s Armpit Fat, Exactly?
Doctors call the armpit area the “axilla.” Most of the time, armpit fat is just subcutaneous fat — basically, fat under your skin.
But the axilla is more than just fat. There’s skin, lymph nodes, blood vessels, nerves, muscles, connective tissue, sweat glands, and some breast tissue all crowded together.
So when people ask, “What is armpit tissue called?” — it’s not a simple answer. The area itself is called the axilla, but any visible bulge can be made up of different things.
For example, some folks have extra fatty breast tissue in their armpits (accessory breast tissue), while others simply store more body fat around their upper arms and chest.
What Causes Armpit Fat?
There’s no single cause behind the underarm bulge. Lots of factors come into play.
1. Genetics and Where Your Body Stores Fat
Genetics pretty much decide where your body likes to keep fat. Some people get more around their stomach, others around their thighs, back, arms, or chest.
So if your body prefers storing fat up top, you might get side breast fat, back and underarm fat, fat pockets under the armpits, or fat between your breast and armpit.
That’s why even slim folks can have noticeable armpit fat.
2. Overall Weight Gain
Gaining weight means you gain fat everywhere — chest, back, shoulders, upper arms, underarms.
For most people, back and underarm fat comes from overall body-fat gain plus their genetic tendencies.
Men aren’t immune to this either. It’s all about total body fat and how their body likes to store it.
3. Breast Tissue in the Armpit
Sometimes, what looks like huge armpit fat is actually breast tissue. Some people have accessory breast tissue (extra breast tissue outside the main breast, often in the underarm area).
This tissue can become more obvious or sensitive during puberty, your period, pregnancy, or breastfeeding. Some normal breast tissue just stretches out toward the armpit, too. So what looks like “boobs under the armpit” sometimes can’t be solved just by losing weight.
4. Loose Skin
A skin flap under the armpit can get mistaken for fat. Aging, major weight loss, pregnancy, genetics, or just less elastic skin all play a role.
If your main issue is loose skin, losing more weight won’t necessarily get rid of it.
5. Bra and Clothing Fit
Tight bras don’t cause fat, but they can squeeze tissue so it looks bigger or more obvious — think too-small cups or tight side panels.
Before you start worrying about your body fat, make sure your bra actually fits.
Why Do I Have Armpit Fat Even If I’m Skinny?
You don’t need to be overweight for your armpits to show a bulge. Even a skinny armpit can have a fold or small spot because of genetics, how your body stores fat, breast shape, accessory breast tissue, loose skin, muscle, or the way your bra fits.
Your weight isn’t the only thing shaping your underarms.
If you’re wondering, “Why are my arms bulky?” keep in mind that muscle size matters too. The back of your arm is home to subcutaneous fat and the triceps muscle.
Can Exercise Truly Burn Armpit Fat?
If only! You can’t choose exactly where your body burns fat. Doing a ton of arm exercises doesn’t force your body to get rid of underarm fat alone.
That’s why spot reduction doesn’t work.
But exercise still helps. Building muscle in your chest, shoulders, back, and arms improves how everything looks, and living a healthy lifestyle helps decrease total body fat.
So, if you want to lose fat around your armpits, a combo of overall fat loss and strength training works best.
How to Get Rid of Armpit Fat Naturally
If your underarm fullness is mostly body fat, lifestyle changes make a difference.
1) Keep a Reasonable Calorie Deficit
Your body burns fat when you use more energy than you take in — but don’t starve yourself. Build meals around veggies, fruits, whole grains, beans, eggs, fish, lean meats, yogurt, and healthy nuts or seeds.
Control your portions, and try to avoid high-calorie foods and drinks that don’t actually keep you full.
2) Get Enough Protein
Protein keeps you full and helps preserve muscle while you lose weight. Eggs, fish, chicken, tofu, Greek yogurt, beans, and lentils are solid options.
You don’t need a fancy underarm fat diet. What matters is consistently eating healthy.
3) Exercise Regularly
Mix cardio with resistance training. Cardio can be walking, cycling, swimming, jogging, dancing — whatever you enjoy. Strength training helps keep and build muscle as you lose fat.
Best Exercises for Underarm Fat
Exercises don’t spot-fix underarm fat, but they do strengthen nearby muscles.
Good ones include:
– Push-Ups: Chest, shoulders, triceps, core. Start with wall or elevated push-ups if you need.
– Chest Press: Builds muscle underneath your chest. Use dumbbells, bands, or machines.
– Rows: Targets your upper and middle back.
– Lat Pulldowns: Works the sides of your back.
– Triceps Extensions: Strengthens the muscles under your arm.
– Lateral Raises: Good for your shoulders.
Combine these exercises with full-body workouts and isotonic training exercises to build overall strength and muscle — this is much more helpful than doing endless armpit exercises.
How to Lose Fat Between Your Arm and Chest
First, figure out if it’s actually fat. If yes, here’s where to start:
- Lose fat gradually all over.
- Get in regular cardio or daily activity.
- Do full-body strength training.
- Add chest, shoulder, back, and arm exercises.
- Keep your eating habits healthy.
- Stick with it.
These tips work for underarm fat, back armpit fat, or side arm fat.
And if the area doesn’t change much even after big fat losses, it might be genetics, loose skin, or breast tissue.
How Do Men Get Rid of Armpit Fat?
Men get underarm and back fat, too. There’s no guy-only exercise — it’s really about eating healthy, doing cardio, and resistance training.
Include exercises for your chest, back, shoulders, triceps, biceps, legs — train everything!
Whole-body training beats just working your arms.
How to Lose Underarm Fat Fast
Honestly, there’s no safe way to melt underarm fat in a few days. Watch out for gimmicky products promising instant results: fat-burning creams, detox drinks, sweat belts, weird supplements.
True fat loss takes time.
You can smooth the area quicker by wearing better-fitting clothes or a supportive bra, but lasting change needs consistency.
How to Hide Armpit Fat
If you just want things to look smoother, fit really matters. Look for bras with wide side panels, full-coverage cups, supportive bands, smooth sides, and comfy straps.
The right bra holds tissue more evenly under clothing.
If you’re eyeing a halter top but feel iffy about your armpit bulge, go for a size that doesn’t dig in at the sides. Wider side coverage and supportive undergarments help too.
And hey — skin folds when you move. It’s totally normal.
Can Underarm Fat Be Removed?
Yes. If lifestyle changes aren’t cutting it, medical or cosmetic procedures are an option — but which one depends on whether you’re dealing with fat, loose skin, or breast tissue.
1- Armpit Liposuction
Liposuction removes concentrated fat deposits through a small tube (called a cannula). It’s for folks who have stubborn fat and stable body weight. Risks include bruising, swelling, infection, sensation changes, uneven results, scarring, and asymmetry.
Remember: liposuction is for contouring, not weight loss.
2- Surgery to Remove Fat Under the Armpits
This can mean surgical excision (cutting out tissue) instead of liposuction alone. It’s for significant accessory breast tissue, excess axillary tissue, glandular breast tissue, or loose skin. Sometimes it combines both liposuction and surgical removal.
A plastic surgeon can help figure out the best approach.
Fat, Loose Skin, or Breast Tissue?
Before deciding how to deal with underarm fat, try to pinpoint what’s causing the bulge.
Ordinary fat feels soft and changes as your weight changes. Loose skin is thinner, maybe hangs or folds, especially after big weight loss. Accessory breast tissue feels denser and gets tender or swollen with hormone shifts.
It’s not always easy to tell at home. If you’re unsure, ask a doctor.
Is a Hard Lump Under the Armpit Normal?
Don’t just assume a fatty bump under your arm is harmless armpit fat.
A hard lump could be something else. According to Cleveland Clinic, armpit lumps can be linked to swollen lymph nodes, cysts, skin infections, lipomas, and other conditions.
If you notice a lump that’s new, hard, fixed, painful, growing, or just won’t go away, get it checked. See a doctor if you have one-sided swelling, skin changes, nipple changes, discharge, redness, or weird breast changes.
Frequently Asked Questions
Q. How do I lose armpit fat?
If it’s just ordinary body fat, gradual fat loss through eating well, being active, and strength training helps. You can’t make your body burn only armpit fat.
Q. How do I get rid of underarm flab?
If it’s mainly fat, losing fat overall helps. Hanging skin, though, doesn’t always respond to more weight loss.
Q. What causes side breast fat?
It’s usually genetics, weight gain, breast shape, accessory breast tissue, or loose skin.
Q. Can underarm fat be removed?
Yes. Liposuction is an option for fat, but surgical removal handles excess breast tissue or loose skin.
Q. How do you get rid of back and underarm fat?
Focus on overall fat loss — healthy eating, cardio, strength work for your back, chest, arms, shoulders.
Q. What if I have a hollow armpit?
It’s probably just your natural anatomy, and might stand out if you lose weight or muscle. But sudden changes or a difference between sides warrant a checkup.
Bottom Line
Armpit fat is normal, and it doesn’t mean you’re unhealthy. Genetics, overall body fat, breast tissue, loose skin, hormones, and clothing all shape your underarms.
If it’s plain old body fat, gradual fat loss through good food, exercise, and strength training helps most. Exercises strengthen your chest, shoulders, arms, and back, but won’t target one spot.
If you’ve got persistent bulges, loose skin, or extra breast tissue, medical treatments like liposuction or surgery can be options.
And most importantly — don’t ignore lumps that are hard, painful, growing, or unusual. That’s a job for a healthcare professional.
References
- Cleveland Clinic.
Armpit Lump: Causes, Diagnosis & Treatment
- American Society of Plastic Surgeons.
Liposuction
- American Society of Plastic Surgeons.
Liposuction Risks and Safety
Medical Disclaimer
This article shares information for educational purposes—it’s not medical advice, diagnosis, or treatment. If you have health questions or concerns, talk to a qualified healthcare professional. Don’t ignore or put off professional advice because of anything you read here.
