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Is back fat normal? Your 5 top sports bra questions answered.

I have a back fat roll- is my sports bra too tight? Why does my sports bra underband roll up? Why do I get red marks from my shoulder straps? Welcome back to our series of bra fit myth busting blogs!

Compiled from the most common questions we get asked here at KnockerLocker during fittings. Keep reading to find the answers that will help you find your optimum sports bra fit and support.

“My underband flips over and rolls up- is it too tight?”

While having your band flip over or roll can be frustrating, it is completely normal. Many sports bras have particularly wide underbands (especially non-wired sports bras). This is to provide security and support. However it does make them more likely to flip up as we move about.

The band rolls, not due to the band size being too small, but due to a combination of our body shape and build. 

It happens to women of all shapes and sizes because we naturally have a bit of soft padding around our ribs. This can push against the underband and cause it to flip up as we move. Just like a waist band can flip over or roll when we sit down.

“My underband is too tight because it leaves marks.” 

80% of the support provided by your bra comes from the underband. It needs to be a snug firm fit. If it is not, you are essentially just hanging your boobs from your shoulders via the straps. Not good for your back or neck.

Ever peeled off your skinny jeans and seen red seam marks on your legs? Did you ditch them and get some flares? Marks from clothing happen. It does not necessarily mean the fit is wrong.

Your underband on your sports bra should be the same measurement as your ribs, or 1-2 inches more (see our fitting guide and bra size calculator.) Your should be able to do it up easily. It should not rise up when you lift your arms up. It should not lift upwards at the centre back. 

It is important to note there is a difference between a comfortably firm band and a constrictive one. If breathing becomes problematic, it is too tight. 

“My bra gives me a back fat roll- is it too small?”

80% of a bra support comes from the firm fit of your underband. If the fit is right and you are not waif thin, you may well get a bit of a back fat/ skin roll.


It happens to women of all ages, shapes and sizes. Do not fear the back fat. The most important thing we are after in a sports bra is firm support and comfort. This means we can exercise in confidence and with pain free breasts.

DO NOT be tempted to get a bigger back band size to minimise back fat. You will end up over tightening the shoulder straps for added security. This leads to red marks, back and neck pain.

Look for a sports bra with a wide underband which can help minimise the back fat spillage. Runderwear Power bra  and Pure Lime athletic are fabulous options. Alternatively look at the Enell Sport bra. Specifically designed for bigger busts this bra features a full back and is great for back fat concerns!

“My bra is gaping so the cups must be too big.”  

If this is the case on both cups, yes your cup size is probably too big. Your breasts should fill the cup space but not overflow. However, most of us have one breast bigger than the other. 

We generally advise fitting your bra to the larger breast, meaning on the smaller side there can be a bit of spare fabric. This results in wrinkling, or gaping in moulded styles.

Many sports bras deliver support through a snug fit around the breasts and a degree of compression. If the cup is too big then we miss out on some of this support. So if we are asymmetric, what are our best options?

Look to a hybrid style non wired sports bra. These feature individual cups with an additional compression layer. Our best seller for asymmetric ladies is the Anita air control delta. With incomplete pads and a compression layer it keeps both breasts encased and supported.

Other options are the Runderwear Power and Pure Lime athletic. Lastly, think about the Enell Sport bra. This is solely based on compression fit and so works well for uneven sized breasts.

“I get red marks and achy shoulders from my straps- what can I do?”

Should straps are the number one point of complaint in sports bras. Either they slip off, leave red marks, are too narrow or cause should pain.

Your shoulder straps are there to keep the bra in place, most of the support should come from the underband.

If you are getting red marks from your straps and they are digging in it is because your underband is likely too loose. This means the shoulder straps are being over tightened to do the heavy lifting.

Many sports bras feature a racer back shoulder strap orientation. This contributes to an added feeling of security but can also cause achy shoulders when worn for long periods.

Look to convertible shoulder straps- these can be worn regular style and then clipped together with a J hook when added security is needed.

Another great option is the Runderwear Power bra (again!) The straps sit halfway between racer and regular. Meaning they won’t slip off but will not press down on your trapezius shoulder muscles either.

Still got questions?

If you are in need of more bespoke advice on what could be the best sports bra for you, book an online fitting and chat to us in person!

Remember KnockerLocker donates 5% of the sale price of every bra to Pink Ribbon Foundation, helping those whose lives are affected by breast cancer.

racerback panache sports bra
enell sports bra in black camo. Great for containing back fat!