For everyone though, outside just Keto.. sugar and (too many) carbs is bad. Make smarter choices to stay away from that "extra size of fries" and watch your calorie intake daily and you're good.
For example, an obese person can literally loose hundreds of pounds just by eating one pizza per day. It's not the best choice, and I would not recommend it at all, but a calorie defecit vs what you require is the #1 key to start using extra fat as energy.
Figure out your BMI and pick a healthy calorie defecit and you can just eat at or under that number and not feel like you're starving if you do it right. My advice is to mix in 3 days or excercise, and don't ever look at something like the "1200 a day calorie diet". You're more likely to fail a strict diet like that and feel hungry.
The idea is to enjoy foods and life still, even cheat sometimes.. but own up that you had a cheat day and take a walk or jog for an extra 30 minutes to make up for it. If you set out to make it work, you'll be just fine.