The trouble with any food studies is you do not know what else the people are eating. You can not live on grapefruit alone. If I was eating grapefruit and not eating a whole bunch more of food Id lose weight and Id reduce my glucose readings. I hear lots of us saying Ive cut my bs reading because Ive cut my carbs. In reality I would have expected this. If you do not put the carbs in then were would the glucose come from if you do not increase your proteins. Fats do not produce glucose. Its bound to be lower. The real test is if we raise our carbs long term does the glucose reading also rise? Ive seen plenty of people reduce their blood sugars to become non diabetes but how many of those are back to the eat well plate 180g carbs per day or have they just remained low carb eaters?