Matt Lovell: It's a terrible time of year to think too much about being fit and healthy and eating all the right things. We always recommend a day off a week from whatever programme we put our clients on, and for Christmas this is extended to a week.

Taking one day off gives you an achievable short-term aim and makes it more likely that you won't deviate from the diet too much, knowing that treats await. On a physiological level too overfeeding on one day acts to replenish glycogen reserves, which may be on the low end if someone is low-carbing and exercising regularly. The additional energy can be used on subsequent days to fuel some intensive workouts. This strategy also acts to outsmart the primitive survival mechanisms, which make body composition changes difficult.

Sarah is doing her best to be good but is not going to be a martyr (quite right too!). The exercise is difficult to fit in with all the other social activities, but to maximise her return for effort she is getting up a little earlier to train on an empty stomach before breakfast a few days a week.

Following this, a hearty breakfast of two poached eggs on wholemeal toast with salt and pepper to taste takes the winter chill away somewhat. The rest of the diet is improving generally too; we're edging Sarah toward organic produce and filtered tap water - something she was little sceptical about.

Organic meat and dairy are particularly important, as many toxins are stored in the fats and the taste is better too. Take home message this week: more water, more fish and more early morning cardio.

We measured a 3 per cent drop in Sarah's body fats this week.