If you just want to lose weight than any diet will do. Cut calories, cut food groups, eat just natural foods, eat pre-packaged diet food, eat just meat and eggs or eat when you are hungry and stop when you are full - they all work.
But if you want to lose fat and keep your muscles than you have to be more conscious of the types of food you are eating. You need to eat enough calories, enough protein, enough carbs, and enough fat to keep your metabolism burning and your gym sessions firing.
But there is more to a diet than just losing fat and retaining muscle. It is not just about how much BF% you end up with.
A healthy nutritional program addresses the following issues:
Energy - do I have enough energy to get through my training and my daily tasks without feeling exhausted?
Hormones - does my skin/hair look healthy? Are my PMT symptoms and period cramps better/worse? Do I have fairly stable moods?
Bodily functions - am I more/less regular? Do I have an upset stomach? Does it take longer to recover from training? Am I getting cramps more/less than before? How are my migraines? How often do I catch a cold?
Lifestyle - do I have the time to prepare my meals? Do I enjoy cooking or would I prefer not to have to do lots of food preparation? Will my family/friends/partner eat this food? Can I afford the grocery bill? Will I be happy shopping more frequently? Do I want to weight, measure and log all my food?
Appetite - do I feel hungry all the time? Does this diet increase/decrease my appetite?
Enjoyment - do I look forward to my meals and feel satisfied afterwards? Do I enjoy eating this food or do I force it down because it is 'good' for me?
Flexibility - can I eat out on this diet? Can I eat this way when I am away from home? Can I take a day off for a special occasion? What will I do if I get sick?
Plan B - Is there a strategy to quickly recover if I go 'off plan'? Is there a contingency plan? Are there different phases depending on my progress? Is there a 'hungry day' option?
Deprivation - does this diet restrict foods that I absolutely love? Can I live without ____ for the rest of my life? Does abstinence appeal to me or send me into a binge?
Emotions - do I feel better as well as look better? Am I happier living this way than I was before? Am I crying/getting angry more/less than before?
Sleep - am I sleeping better or worse? Do I wake in the morning full of energy or drag myself out of bed?
and most importantly of all
Compliance - can I do this for the rest of my life? Can I modify this diet into a way of life to maintain the leanness I have achieved? Is the amount of discipline/effort/focus worth the rewards? Do I have enough information to make adjustments if my clothes aren't getting looser?
Of course it is primarily a balancing act. You can't expect to feel full all the time, eat all your favourite high calorie foods, sleep like a log, be constantly cheery and never get sick while losing fat. You have to negotiate a strong sustainable position that gives you the best possible outcome.
For example - low carb completely takes away my hunger AND my ability to train. I therefore choose a level of carbs somewhere in the middle that means I can train hard [but not as hard as I could on a high carb] without excessive hunger [but more hunger than I would have on low carb]. I also can't imagine giving up chocolate or ice cream so I eat 'diet' versions almost every day even though sticking to natural clean unprocessed food would make me healthier and possibly leaner.
So when you choose a diet for your 2009 transformation, don't just pick one that guarantees weight loss. Choose a nutrition plan that will strip off the fat while keeping you sane on all levels. It might be any one of the millions of eating plans out there, but make sure that you choose one that benefits all of your life, and not just the number on the scale.
If you want a healthy, enjoyable way to burn fat and feed your muscles I can highly recommend this program.
And if you can't find anything official that works for you - make up your own!