Large thighs appear to confer health benefits, not risks. A study reported this month shows that people who have small thigh muscles, independent of how much fat they have in their bellies, are at increased risk for premature death, particularly from heart attacks ( British Medical Journal, September 2009). 2800 men and women aged 35 to 65 had their thighs measured and were followed for ten years. Those whose thigh circumference was below 24 inches (60 cm) were at increased risk for death from heart attacks.
Other studies show that having very low body fat is also associated with early death, as are being overfat or storing fat primarily in the belly. If you store most of your fat in your belly and have very small thighs or buttocks, you are probably already diabetic or prediabetic and at significant risk for a heart attack. Another interesting study on benefits of thigh fat Why belly fat is risky