I would agree that when talking about diet/activity, 85%/15% is fairly accurate.
I would disagree that all you have to do is eat less. The 1 thing you need do is learn that what people have been taught about dieting for the past ~50 years, is 100% wrong. It's not about calories in/ calories out. Your body doesn't count calories. It is all hormonal and the #1 hormone you must concern yourself with is insulin.
You want to eat in a way that is going to, not only, spike insulin less but also a way that is going to affect insulin less often. Overweight people try dieting constantly and the more often they do it, the harder it becomes to lose weight the next time. When one reduces calories on this standard western high carb diet, they are told to eat several little meals throughout the day. That is the worst advice ever and couldn't be more wrong. When raised, insulin blocks all stored fat from being used as energy. It can then only store more fat. If you're eating 5 or 6 times during the day, that's 5 or 6 times every day that you're affording your body more opportunity to store fat.
This is why IF and keto have both been found to be so effective. They address the insulin straight on and give the body more time to burn fat than to store it. People just hate on both IF and keto because both go against the grain of what they've been brainwashed with for the past several decades.