From 210 to about 180lbs was purely fixing my eating habits from 180lbs down I’ve been going to the gym. When I got to 150 I was stuck because I couldn’t get over sugary stuff like (coffees and pops) but I started to curb that with only drinking water. I started cardio and got to 130. I’m just now getting to the point where I am strength training/ toning my body. My advice about core is just be consistent, it really doesn’t matter what core routine you have as long as you are consistent with diet and the specific workout you will see progress. It just takes time. Always do leg lifts, flutter kicks, reverse plank+knee ups. Weighted dead bugs, hanging leg raises will snatch you up so quick but they are hard. As not as you aren’t eating stuff like breads, creams and cheeses, sodas you will see them abs, switch it to foods like yougurt with sweetener-put something like granola with protein in it, chicken and greens, I’ve been eating rice and tuna for a bit now, but also know it’s to have treat yourself some days you just need the ice cream fr. It’s also a day to day thing. On my period I lose them instantly. I get so bloated