I'm not going to get into the argument about carbs vs. fat. My experience is that fat gets a (mostly) bad rap, and simple carbs have more to do with weight loss than anybody will admit. The Excellent Wife (TEW) thinks I've gone too far in this direction. YMMV.
The rules I follow are these:
- Exercise hard six days per week (or seven);
- Don't eat crap;
- Weigh yourself every day, and keep track.
As far as what I eat: People who've been on rides with me know I eat all kinds of muffins, cookies, and whatever; I drink sugary stuff. At my in-laws', I eat lots of good food, and lots of sugar and white flour. But I don't do that every day; I save it for either when I need the calories (like long rides), or when the quality is really good (I'm related to some excellent cooks). TEW and I live a much more abstemious life from day to day.
Weighing myself daily: I use the Hacker's Diet computer tools. The Thysell spreadsheet I linked to four years ago no longer works, and the Excel tools on the Hacker's Diet page have not been updated in years (so I can't make 'em work with current versions of Excel), but the online program works great. As I said in the post from 2010, the fact that it keeps track of the trend means that you don't get to give yourself a pass on a day when your weight is temporarily down, and you don't have to despair if you're high weight is an anomaly. You can also use the graph to see if you've really been stable, or if you're slowly trending up again (as I have done). Daily progress checking makes it a little harder to lie to yourself.
The careful eye will note that the above numbered list starts with two. There's a reason for that. My experience is that most people will start a regimen, and fall off. They'll go on a diet, with the intention of going back to their previous ways when they've hit goal. They begin to exercise, and then skip a day, and then skip two, and then the treadmill is a laundry rack again.
The most important thing is that you've got to want to do it.
That said, if you really want to change ANY behavior - whether it's losing weight, learning something new, or whatever - I have two suggestions: first, hang around with people who do what you want to do. We tend to pick up the behaviors of the people with whom we associate.
Second, make it a habit. That takes time: more than a week, more than a month; probably more than three months (despite what the "change your life in three weeks" behavior gurus tell you). When intention won't get you moving, when fear won't get you moving... when nothing else will do it, you'll do it because of habit; you'll do it because that's what you do.