Assistance required in finding initial users

We are developing a product and want to conduct short survey among initial users. For this job you need to find people from US or UK who are using Calorie counting apps and ask them to fill 2-4 mins survey which will be provided to you. Survey just need 30-50 respondents. It's not a fake survey filling project, you need to do actual market research. You need to find real people in target market and need to show proof how you have done that. We can increase the project amount if it goes well.