Adrian Sutil has revealed that he did not eat for "two days" amidst concerns that his weight is costing him valuable tenths out on track.
This season Sutil has often spoken of his struggles in light of the new 691kgs minimum weight.
Not only is the German one of the heavier drivers on the grid given his height but Sauber - who are introducing a lighter car this weekend in Spain - were also battling to get their C33's weight down.
This led to 31-year-old Sutil going days without eating food.
"I was testing it a little bit here and there. Two days, no food, only drink...I tried," he revealed at the Circuit de Barcelona.
"It was not easy but interesting what the reaction is. I'm eating now again, it's better."
The German admitted that the lack of food cost him strength while adding that not eating was his decision alone.
"I couldn't do much sport because the power was missing. I do it because I want to go on the limit just to make sure I did my maximum. I don't want to be in the car and say, 'Oh, I could have done more'.
"I could feel there was a limit where I hadn't the power anymore, the strength in my mind - you get stressed quite early - and you don't want that. It's just important to know your body quite well.
"I tried it but I'm still alive so don't worry too much. It was my own decision, this is most important."
As for the new lighter parts that Sauber will introduce in Spain, Sutil said: "It's a very good step I think in every area: the weight, the aerodynamics and also the power train has improved.
"I believe in it and especially tomorrow will be an important day to test it all to make sure everything works fine and I expect a good performance improvement throughout the race weekend.
"Our expectation is normally always to score a point or more and I want to be back in this area. So hopefully it's enough."