Gordie, the reference you may have seen online concerning carbs is the basis for the low sugar lifestyle (I refuse to call it a diet, since that always fails).
Nutrition labels will (at least here in the U.S.) provide carbohydrates, fiber and sugars (as well as some other information). The point is to consider fiber as beneficial so the simple equation is to subtract the grams of fiber from the grams of carbohydrates and divide that figure by the constant of 5.
The grams of sugar in a teaspoon is often said to be 4.0 grams. This is a number that is actually being rounded down to make it easier to use for quick calculations. To give you an exact number to the grams of sugar in a teaspoon, the U.S. Department of Agriculture, who are also the ones setting the dietary guidelines in the United States states the exact number is 4.2 grams per teaspoon of sugar. The point being that for each 20 teaspoonsful there is almost an extra teaspoon in difference from the correct amount calculated at 4.2 grams. Hence, rounding up to 5 is favorable.
This takes in to consideration that natural sugars that occur in carbohydrates are fine, but manufactured sugars are a real problem to health.
Most health professionals recommend a maximum of about 10-13 teaspoons full of sugar for men and 9-11 for women per day. Use the formula the next time you have, say, a bowl of cereal. It's amazing how much sugar we consume a day without even thinking about it...
Lastly, don't be fooled by the label that lists "Sugar Alcohols:.. when the product is advertised as "low sugar" or "no sugar added"... one site says "The sugar alcohols commonly found in foods are sorbitol, mannitol, xylitol, isomalt, and hydrogenated starch hydrolysates. Sugar alcohols come from plant products such as fruits and berries. The carbohydrate in these plant products is altered through a chemical process. These sugar substitutes provide somewhat fewer calories than table sugar (sucrose), mainly because they are not well absorbed and may even have a small laxative effect.
Many so-called "dietetic" foods that are labeled "sugar free" or "no sugar added" in fact contain sugar alcohols. People with diabetes MISTAKENLY think that foods labeled as "sugar free" or "no sugar added" will have no effect on their blood glucose. Foods containing these sugar alcohols need to have their calorie and carbohydrate contents accounted for in your overall meal plan, as it is carbohydrate that raises blood glucose levels..."