The individual had been following a strict detox and then over christmas had eaten lots of foods they'd been avoiding on the detox, this made me suspect that infact the swollen calves were due to water retention due to eating foods that had been avoided during the detox.
The converse is also true - you can lose a whole shoe size if you cut out a food to which you are intolerant. This frequently happens to clients on a detox programme or very clean diet such as my bootcamp regime - infact I had to put some insoles in my shoes yesterday (although the cold also shrinks your feet).
When I first stopped eating gluten I lost half a shoe size which never came back (although probably would if I started eating gluten again) and so I had to give my entire shoe collection away to some very happy friends (I was broken hearted).
The reason for this is that if your body has become intolerant to a food it means that it has decided that particular food is going to do you harm and so it mounts an immune response. This can lead to bloating, skin rashes, breakouts, other allergies, sneezing, inflammation and elevated stress hormones.
The body tries to reduce the damage by diluting the food in the body and to do this retains water in the cells. So if you eat a food you're intolerant to you can hold up to 6Lbs of water weight. If you cut this food out for three weeks you will then often lose this weight and as fluid retention is common in your feet and lower legs this may cause your feet to shrink.
Incidentally if you lose weight and then hit a plateau above your ideal weight, despite eating very healthily and exercising, then an intolerance and associated water retention maybe the issue. It is also likely if you often wake feeling slim but by the end of the day feel bloated and puffy.
So if you're following any kind of detox or elimination diet and find your shoes a bit slippy then it means you're onto something and have cut out a food that you are intolerant to (although this also happens with serious weight loss). Don't ignore this symptom - try and work out which food was the culprit and limit your intake, as eating that food regularly could be damaging to your health ... the clue is in the shoe!