It is a great first step. But it is complicated.
People don't like being uncomfortable and we all actively avoid pain. Exercising at a level that significantly impacts weight loss is hard. It can be extremely uncomfortable and even painful at times. We are soft and we have a universe of terrible pre-processed foods at our disposal. It is just a fact of life that people actively avoid uncomfortable situations and so much of modern life is all about YOU being the star of your own universe and your comfort.
I think exercise and doing physically uncomfortable things consistently and at a high volume (with appropriate and healthy ramp up, of course) can shock a system into being able to cope with discomfort, the kind of discomfort required to break through previous weight loss barriers and habits. Along with understanding the problem and displacing unhealthy eating habits (and those habitual triggers) I think a lot more people would be successful at sustaining weight loss. A very small percentage of people will sustain weight loss (studies put it at 5-20%).
The sayings and weight loss facts are all missing a very large component and that is focusing on how to make weight loss sustainable per individual. No one wants to hear "You are about to embark on one of the most difficult tasks human beings in western society regularly undertake. Your chances of a failure are very high. In order to succeed you will have to learn to be uncomfortable. You will have to dedicate time and real effort to this over a course of years." That said, there are plenty of diet only programs that can sustain weight loss as exercise heavy programs.
http://ajcn.nutrition.org/content/82/1/222S.long -- This is a great look at what things are more or less successful over a longer period. One of the most interesting things is that triggers (medical events) are very good at starting and sustaining weight loss. To me this is one of those system shocks that can tilt the balance in favor of "okay, I have to tolerate this lesser discomfort now because I now I will face a much greater and debilitating discomfort in the future". Only, unhealthy eating for most people is almost always a major medical event 10-20 years down the adult road. It takes it being shoved into the forefront of the mind before people take it seriously. Anyway the summary is gold:
"Findings from the registry suggest six key strategies for long-term success at weight loss: 1) engaging in high levels of physical activity; 2) eating a diet that is low in calories and fat; 3) eating breakfast; 4) self-monitoring weight on a regular basis; 5) maintaining a consistent eating pattern; and 6) catching “slips” before they turn into larger regains. Initiating weight loss after a medical event may also help facilitate long-term weight control."
That is it. I think you need to have a plan in mind that incorporates all of these and I think from the outset they should all be a part of your weight loss habits for the most success. My own experience bears this out, having beaten the odds by (unknowingly) doing almost all of these things save for having a medical trigger (I did have a "looking in the mirror" type trigger somewhere after my first son was born and I realized I was an out of shape lazy ass that could never keep up with my kids at the rate I was going). I am pretty passionate about this topic because so much of my family got stuck in the Jenny Craight / Weight Watchers / Atkins -- just do this one thing and lose weight habit and it has never worked. I think folks on hacker news that have high enough emotional intelligence can probably work it out with just food management, but I think long term that is just as hard as trying to exercise out your bad habits. These strategies all go together to address all the areas people are likely to fail creating a safety net to prevent habit relapse.