Could someone expand more on this? I haven't heard much about the downsides to "low-fat" foods before.
He's possibly referring to sugars added to low fat foods to make them taste better.
There seems to be a myth that fat is bad, so food companies produce all this low fat stuff that is more often that not laden with sugar. Excess amount of sugar is probably more harmful than excess dietary fat.
Then there's the low fat margerine spreads made from hydrogenated oils that they try to sell us. Give me real butter any day of the week!
My general approach to diet is to eat things as close to their original state as possible. I'll take natural yoghurt over flavoured low fat yoghurt and I'll take real butter over margerine. The shorter the list of ingredients on the packet, the better as far as I'm concerned.
EDIT: The above example is kind of moot for me now as I rarely eat dairy.
The thing that stands out the most to me is the bit about fluid/water.
Some days I don't even get to a tap except to fill the kettle up so I really need to push myself to remember water over a cupper from now on.

Still get it to some degree but not as bad.
