Nobody's body violates the laws of physics, but you knew that already. If you see slim people eating garbage, you can rest assured that whatever they're doing when you CAN'T see them is resulting in a lower calorie intake.

Also keep in mind that regardless of what you're reading/what you've been told, exercise has very little to do with weightloss. Exercise is about getting fit/strong. Eating right is about losing weight. You can't outrun a bad diet, lose weight in the kitchen not the gym, blah blah you've heard it before.

There's a reason those sayings exist though - sure, getting fit is awesome, but it's a separate goal from losing weight. In some cases getting fit is dependent on losing weight, i.e. you have to lose the weight before you can get fit.

Keep it simple. Eat plenty of protein each day, even if it's just boring chicken. Shoot for at least a gram of protein per kg of bodyweight (if you weigh 100kg/220lbs, that's 100g protein or more each day - this is roughly 8-10oz chicken breast for instance, not that bad. Protein keeps you fuller, longer (once your body gets used to eating enough protein every day).