Are there GOOD and BAD carbs?

TRADITIONALLY , starches (think bread or rice) were considered “good” because they take longer to digest than the simple sugars in sweets – the so called “bad” sugar. But more recent research has shown that certain starches, such as those you find in processed breads and most commercial breakfast cereals, offer little nutritional advantage over simple sugars.
Our bodies convert these starches to glucose at such high speed that in terms of the “sugar high” you get from them you may as well be eating pure sugar. You should never also assume that ‘wholemeal’ means unprocessed. Instead, look for bread that contains whole grains.

Why are some carbs less fatening?

In theory, all carbs should be equally fattening. But the body doesn’t use all carbs in the same way. For example, the unfermentable carbohydrates in celery fibre don’t get digested in the stomach. Instead, along with the other fibre-based carbs, they “slip through” the body’s digestive system before they can turn into love handles.
The proportion of carbs in a food also has a bearing on how ‘fattening’ the food is. So fruits such as apples, with their high water content, do less damage to your hips than an equal weight of sweets, cereal or pasta.