There are a lot of theories out there surrounding sit-ups, crunches, and various other abdominal work. While some people swear by them in order to get the ever-elusive six-pack abs, others believe that sit-ups don't help for anything but strengthening the core. To end this age-old debate, POPSUGAR spoke to Casi Reali [1], a SoulCycle and fitness instructor in the New York area with pretty incredible abs (I know, I've seen them), about the best way to work that core to the . . . well . . . core.

"To be completely honest, if you want to burn fat you need to always have some type of cardiovascular activity. SoulCycle [2] anyone? But really, sit-ups are also great in conjunction with cardio," she said.

Reali noted that doing exercises like sit-ups, crunches, and variations of the work will help to strengthen the abdominals and build muscle. This, in turn, will help burn fat faster than just cardio exercise and will tighten the belly fat faster.

And, Reali added, the abdominal exercises that work more than one group of core muscles are a better way to build up those muscles. She favours the Russian weighted twist [3], as it also targets the obliques, and plank hip dips [4], as she noted that anything plank-related is great for building up the muscles in your core.

"Mix some burpees, mountain climbers, or jump squats in there, and you'll be burning up in no time," she said.

But if you're looking to really sculpt those abs, Reali said that watching your diet is key to shedding and shredding.

"The oldest saying is that abs are made in the kitchen and that's mostly true," she said. "You always need a balanced diet. Anything with added sugar, stay away from it. Sugary juices — pour them down the drain. Limit your dairy intake or completely take it out, substitute almond milk over regular milk. Drink lots of water to hydrate and flush out your body. You need to have a diet [5] filled with high fibre, protein, and healthy carbs."

But, she said, not depriving yourself is also part of the balance, just be sure to make up for it. "Balance makes perfect, but also, if you want a slice of pizza once in a while, eat the damn pizza! Just add in some more cardio," she said.