Sauber's Adrian Sutil revealed he trialled abstaining from food entirely as he battled to lose weight for 2014.According to Germany's Auto Motor und Sport, Sutil (75kg) is 13kg heavier than his featherweight team mate Esteban Gutierrez.Sauber, running Sutil's car without a drinks bottle so far in 2014, has managed to cut "substantial" weight from its Ferrari-powered C33 for the 2014 Spanish GP on May 11.BATTLE TO LOSE WEIGHTReports indicate it could be as much as 15kg lighter.Sutil said: "I don't want to say numbers but it's important that we are close to the (minimum) limit now. You can never build 'too light' a racing car."Sutil's disadvantage will continue in Spain as only Gutierrez is slightly beneath the FIA's mandatory limit, allowing him to position ballast around the car to improve handling.Sutil has been critical of the sport's reluctance to further increase the weight limit, as it has driven naturally heavier drivers to ramp up their dieting regimes.He told reporters that he has experimented with fasting: "I was testing it a little bit here and there. Two days, no food and only drink. It was not easy but interesting what the reaction is. "I could feel there was a limit where I didn't have the power any more, the strength in my mind. It's just important to know your body quite well. I tried it but I'm still alive so don't worry too much.