Great article. Wanted to add that while it's true diet is the single most important factor for losing or gaining weight, exercise, should be practiced alongside a good diet for best results.
Increased muscle mass also boosts metabolism as the energy demand of muscles is higher therefore more calories are burnt in day-to-day activities and alongside with aerobic training increases fat oxidization (ie uses fat stores instead of sugar in the blood) leading to quicker weight loss and a better look overall.
There is also substantial evidence showing the benefits of exercise in reducing the risk of multiple cancers, lowering cholesterol, blood pressure, stress, psychological benefits etc
So yup diet is the most important thing but exercise would be highly recommended along with it! You don't need much either lifting weights 3x/week to failure for 30mins/session and 20mins of moderate intensity aerobic exercise 3-4/week is great for a large proportion of people