I work on a simple principle that how much fat/protein I eat depends ow whether or not I need to I need to lose weight, maintain it, or gain it. It's a bit more "elaborate" example of what Totto has told you!
On a very low carb diet your body will switch over to burning fats (AKA ketosis). The fat you eat, and/or have stored in your body is used to replace the energy you would have been getting from carbohydrates.
So:
- My meter tells me whether or not I'm eating about the correct number of carbs for my target glucose levels
- If I'm losing weight and need to, then I'm eating correct amount of fat/protein, but if I don't need to lose weight then I need to eat more fat/protein
- If I need to lose weght, and I'm not - I'm eating too much fat/protein to lose more weight, but am eating the correct amount for my weight to remain static
- if I'm gaining weight then I'm (obviously!) eating too much to either lose any or for it to remain static so need to eat less accordingly
- if I'm any of the above but getting hungry, then I may need to eat more fat and less carbs or protein
I have a husband who likes to be in charge of shopping and main meal cooking, so it easiest for me to do the above rather than try to get things weighed and measured and calculated...
As I usually eat (very) low carbs - between 30-50 g a day, I normally test before my meal and 2 hours afterwards, but if I ever eat something I'm doubtful about or am aware may cause a spike, then I'll also test 1 hour after eating. Generally a lower carb meal may show a spike at 2 hours, fast acting carbs such as sugar will spike more quickly (thus the 1 hour test) and slow acting ones, (e.g. pasta??) will react more slowly, so sometimes people may also choose to retest at longer intervals such as 3 hours after a meal. If I'm wrong here someone will correct me!!
Robbity
PS High fat doesn't necessarily mean you need to scoff bucket loads of the stuff, just enough to fill your energy requirements and keep you from being hungry. Mt (and many others) LCHF tends to be Low Carb Higher-Fat-than-previously.