Leaving it until a few weeks prior to your flight means one thing - water weight. People tend to go on these crazy starvation diets which only tend to lose muscle tissue and water, therefore giving you a poor 'beach body'. Muscle is what gives a body good shape, and by losing that, you're not going to look good on the beach. You may well be thinner and lighter, due to the water loss and muscle tissue loss, but you will notice your weight will increase fairly quickly when you start eating normal food again and drinking alcohol (what many people do on their holidays).
So when should you start?
I would recommend starting in January if your holiday is booked for March/April. This will give you at least a couple of months to train and sort your diet out (especially after Christmas and New Year celebrations).
Some of you reading this may think that's too soon, but many people expect good results far too quick. A couple of weeks of training and eating healthy will not make any noticeable differences to your figure. If you're actually serious about getting into 'beach body shape' for your holiday, then you want to start now.
By giving yourself enough time, you will be able to shed actual fat tissue, build a little bit of muscle and not having to worry about the weight coming back on after a few days of eating food and drinking alcohol.
Don't leave it until the last minute, give your body enough time, and you'll be very happy with the results!
Lee Gregory Fitness