New to forum and myfitnesspal

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Sooo I joined because I need to lose weight, 20 to 25 pounds, and I'm on a weight loss challenge for 60 days at my local Pilates studio. There are 50 of us and whomever wins the greatest % of body weight lost wins $2000. I workout and train hard for 9 months of the year and then I took 3 months off which didn't do me much good. So here I am with the weight loss challenge and I need to lose all the weight by September. I'm taking 8 different classes during the week to cross train and weekends I should be hiking but we've had too much rain so I'm only walking 6 to 7 miles a day. I am now one week into the challenge and lost 3 pounds but I am hungry!!! I am trying to go gluten free just to see what happens and keep my carbs to 100g/day. Right now I just want to win the challenge and lose 10-15 pounds for the 60 days which is a lot since I'm not too terribly overweight. It's hard to stay motivated but I guess what's the alternative- gain more weight? I will just keep slogging through this.