There are multiple fad diets that are popular in the US that boil down to &#x27;low carb&#x27;.<p>I often wonder if it isn&#x27;t anything subtle, just that processed carbohydrates are incredibly energy dense. 100 grams of sugar or flour has twice the calories of 100 grams of beef (prepared bread still has more calories per gram than beef). 100 grams of greens or non starchy vegetables almost doesn&#x27;t have calories.