You wouldn't have to straight up tell them that you are trying to lose weight. You could tell them you are eating healthy and exercising because you want to live a healthier lifestyle. Everyone's bodies are shaped differently, don't feel like you have to look like a model. God made you the way you are out of his own image and likeness. Also, don't be afraid to tell your parents the truth. Maybe you could exercise WITH your parents and help them lose some weight too!
Food labels can help you lose weight, if you know how to read them. Everyday Health says it's important to pay attention to serving size, calories (and calories from fat), fats, cholesterol, sodium, carbohydrates, protein, and vitamins and minerals. Then, you can make smarter food choices like picking up a water-packed tuna rather than oil-packed, which can cut significant calories.
For even more impressive effects on body composition: aim for exercise forms which elicit a positive hormonal response. This means lifting really heavy things (strength training), or interval training. Such exercise increases levels of the sex hormone testosterone (primarily in men) as well as growth hormone. Not only do greater levels of these hormones increase your muscle mass, but they also decrease your visceral fat (belly fat) in the long term.
Salt, in moderation, is a good thing—the mineral is necessary for a healthy heart and brain. But too much salt and you’ll retain water, bloating up like a water balloon. Cutting salt is one of the primary ways to drop extra water weight (one reason you may see a big weight loss when starting a new diet!). Move the salt shaker off your table so you’ll get out of the habit of routinely salting all your food. Then if you taste your food and still really want salt you can still stand up and get some. For more weight loss benefits, add these fat-burning foods to your plate to help you lose weight.