I've run 5/3/1 while losing weight. I've also run more demanding programs under the watchful eye of a coach while losing weight. During both of those times I did remarkably well, losing fat and getting stronger.
I'll echo the dietary recommendations on eating for performance:
- Keep fat lower and carbs higher
- Adjust your total calories so that you are losing the equivalent of 1 lb a week
- Supplement creatine, even with the water gain, it can help give you the edge to keep pushing hard in the gym.
- Work just as hard in the gym as you do now
While cutting does present a head wind, most of us are not pushing so close to the edge of our potential (me included) that you can still continue to progressively get stronger while eating fewer calories.
If you have a scale that estimates body fat, you may see your estimated lean mass shrinking. Do not be alarmed! Not all lean mass is muscle, some of it is water retention, some of it is misreported. In either case, your fat weight should be shrinking faster than the lean mass. As long as you are improving month to month in the gym, you are getting stronger.
From the Performance Nutrition Encyclopedia
One of the things that the Josh Thigpen suggests is a pre/intra/post workout nutrition were you have a combination of quick carbs and protein for each of these.
- Pre-workout: 10-15 g protein, 20-40g carbs, creatine
- Intra-workout: 10-15 g protein, 20-40g carbs, creatine
- Post-workout: 10-15 g protein, 20-50g carbs
Basically, this describes Skim Chocolate Milk very well. Mix a batch with the creatine powder for your pre/intra workout and have some plane after training.
Also, make sure you account for that in your total calorie intake. You can set your daily intake a little lower, and use the pre/intra/post workout to boost the calories where you need them. The goal here is to provide the protein and energy when your body is most prepared to do something with it.