Agreed, absolutely. It requires additional denial of one's urges beyond the urge to sleep-in or hit the barca-lounger after work. That might just be psychological overload for people who are deeply conditioned to poor eating and exercise habits. Ways can be found to rationalize a let-down in discipline. Just look at how many purportedly dedicated runners must have trouble with eating habits around holiday time, they are immersed in a culture that not only revolves socially around eating food but eating calorie-dense food that is laden with sugars and animal fats. Or the commute home takes one past numerous fast food outlets and the like. Realistically, many (most?) people can only really handle focusing on one side of the calorie input/output equation in breaking entrenched habits and while exercise of course provides numerous benefits beyond weight loss, diet is where the lowest-hanging fruit (pun intended) seems to be for simple weight loss and health.