If you’re training for an event eg Ironman, Comrades, Warrior, Berg and Bush, or whatever it may be, focus on PERFORMANCE.

Weight loss goals tend to interfere with performance goals and take priority in our minds. In our misguided quest, we drive ourselves relentlesly in our training, whilst restricting calories to shed that extra kilo. The result is, we lose sight of what we’re training for, performance suffers, we experience burnout, illness, injury and more than likely, weight gain, not weight loss.
Eventually you want to throw in the towel!
So, when training for an event, eat, exercise, prepare mentally and rest in order to optimise PERFORMANCE. Any other goals are secondary. By putting performance first, it is likely you will achieve your weight loss goals anyway – you only have to look at high level athletes to realise that optimal performance will result in the optimal physique.
Sometimes weight loss is an important component of performance. Any cyclists or runners out there will tell you how their times improve when they drop a few kilos. If you need to lose weight, focus on weight loss early on  in the off season or preparatory period (several months out from an event), when training intensity and volume is relatively low. This way you can afford to restrict calories slightly without the detrimental effects on your body and performance. As training intensity and volume picks up however, weight loss goals should give way to performance goals.
A final point:- Have a realistic expectation of the changes you can expect to see in your physique. Don’t for example expect to look like a body builder if you’re training for Ironman – your body has no use for large powerful muscles in endurance events, and your body will undergo physiological adaptations based on the demand imposed on it – so expect to be leaner, more wirery and athletic. (genetic factors also come into play- a conversation for another day).
Goal conflict can be a major distraction when training for an event. Put performance first and other goals second, and watch the PB’s roll in. It is also amazingly liberating to throw out the old scale while you watch and feel your body soar to new heights.