Interesting question GS,
I haven't read the book but Ayurveda says people with higher body temperatures will digest faster. I have a high body temperature and my digestion is very active. You can tell basically the state of your digestion by the colour of the top of your tongue. White or the various shade of white rather than pink is an indicator of indigestion.
The books say that pungent ( hot spicy taste) and heat (which can mean in the case of a raw diet eating at the live temperature of the animal not just out of the fridge or freezer) will increase the digestive power because it raises the temperature of the digestive fire. Too hot a digestive fire will burn the food rather than cook it properly. This will show up as very dark, hard stools and heat related disorders such as cankers, red skin, sore throat, burning feelings, excessive bleeding, temper, anger, etc.
Too low digestive temperatures will result in lethargy, depression, fluid buildup, or dryness, small or underdeveloped body features such as eyes fingers, nails, or conversely very oversized features, chronic weight gain or loss.
Too low a digestive fire will result is sticky, whitish mushy stools.
Some people have variable digestion meaning that it is perfect then they get constipated or have diarrhea.
Proper digestion results in a beer coloured stool shaped like a banana that plops out easily with out leaving residue on your....... ass.
Better to be too heavy than too light up to a point. Depends on what you have ingested to get you there.
Best to be a comfortable weight for yourself, however with children it is better for them to have a bit of excess fat as this promotes growth of everything and most importantly the brain.
Personally I thing that a strictly raw diet is the answer.
There was a study done on aboriginals in Manitoba Canada a number of years ago to determine why they had high rates of diabetes. The conclusion was that they had evolved as HGs to eat a feast or famine diet so when they adopted the Honkey's
ways of a steady diet they were opting for what their body would instinctively have wanted and done well on previously which was the feast part, but the missing part was the famine part, so this chronic overnutrition upset their inner applecart causing diabetes. I would add to that the lack of raw food in their diet.