Training
Peaks have just published a piece on carbs and glycogen.
There is plenty of evidence that if you train hard day after day, your glycogen stores get depleted unless you eat a high carb diet.
Glycogen can be restored without carbs, though - it just takes longer.
Basically fat, protein, and carbs all end up as the same sort of thing in your body, they just get processed at different rates.
If you want hard exercise for over a couple of hours, or you want to keep doing hard exercise many times a week, carbs is the only way to keep up.
Imagine trying to fill your bath with a cup when you have taken the plug out.
The bath can start full, but you just can't get enough water in with the cup to stop it emptying out.
If you only do a few lighter sessions a week, then a lower carb diet can keep up (just as you can fill the bath with a cup when the plug is in!). And lighter exercises use little or no glycogen anyway,
If, once a week or so, you do a hard exercise of say an hours, you can also keep up, because your body has enough time to top up the glycogen again.
Of course, there are wider implications to a high fat diet, such as heart disease.
And there are implications for not exercising.
But most of the health benefits from exercise come from the "medium" level, not the "athlete" level.
What I would urge is that you eat a varied diet with plenty of fruit and veg in there.
(before you get excited about the sugars in fruit - iirc, tomatoes and pumpkins are technically fruits - that's why they have seeds, amongst other things!)
If you do want a high-performance exercise regime, though, it really does have to have quite a lot of carbs - just make sure they are sensible carbs, not just endless refined sugar.
Fruit and veg and exercise - that's what we all agree on.
