This is whats happening:
I'm still growing.
You are thirteen, and say you are classified as 'overweight', so I'll assume you are talking about your BMI and aren't considered 'obese'. Usually metrics like this are calibrated for adults, usually for males and are based on limit studies. BMI is useful at the population level and can be a useful metric in a limit set of individual cases. However, as a young teen, metrics like BMI will not be accurate for you.
Likely, you are going to get heavier simply because you are still growing. If you are concerned about your health or appearance, rather than try and lose weight, try and have your body "grow into that weight". Focus on building positive habits that can help reduce your total body fat, without limiting the energy your body needs to continue growing. At 13, you are likely to continue growing in height, so focus on eating healthy and look at other metrics for your health and fitness. For example, get a bicycle speedometer and track your bike rides, aiming for a better pace each session.
Consider doing some basic strength training that you enjoy
This depends on what equipment you might have access. Even a basic exercise routine like bodyweight squats, push-ups, and abdominal planks will help build beneficial muscle in an untrained individual, and can be made more difficult in a number of ways by repositioning the arms or holding something as simple as a large book. Search on this site for some basic introductory strength or bodyweight routines and see if you find one you like. Track the number of reps and weight of exercises you do and aim to improve every week. Strength is important whether you're a young man or woman. Weight training helps to build fat burning muscle, improves cardiovascular health, increases bone density (which is especially important for women in later life), and can help improves your energy and mental levels.
The key however, is to find exercise you enjoy. While exercise can be tough, and it builds discipline having to work through that, you need to find exercise that works for you. Once you find a program stick with it for a few weeks to see if you adapt to it. For example, while you might not like doing push-ups on day one, or enjoy the muscle stiffness on day two, by week 3 you may begin to enjoy them or enjoy the changes they build in your body.
Eating healthy needn't be difficult or expensive.
Likely, your diet is most likely restricted by what foods your parents buy cook, but when you can:
- Limit foods with added sugars and stay away from soda
- Aim for fresh whole foods that are high in fiber - This includes vegetable and fruits, wholemeal grains and lean meats. At dinner aim for more vegetables and less meat. A playing card sized piece of meet will have the majority of the protein you need for a day. Healthy vegetables such as pumpkin, broccoli, cauliflower, sweet potatoes and leafy greens like cabbages and spinach are high in vitamins and fiber and low in calories. By loading up on these you will feel fuller for longer and give your body the nutrition it needs.
- Limit your snacking - Snacks foods available now days are often loaded with fats and sugars and promote over eating. While even a small handful of nuts is healthy, if you absent-mindedly eat them over the whole of a day they do add up.
- Eat sufficient protein - This includes animal protein such as meat, eggs, and dairy; but also vegetable proteins from nuts, tofu, rice, wholemeal breads, beans and legumes.
- If you are concerned about what you are eating, keep a food diary, but don't overly stress about calories. You are young, and you have one awesome factor in your favour - puberty burns energy and builds muscle (in both men and women) in a way that will make the most seasoned runners, lifters, athletes and dieters jealous.
While you might feel peer pressure about your weight, if you eat well and in healthy proportions you can help improve your health, reduce your body fat and improve your muscle mass without having to worry too much about your actual weight. Also remember, two weeks is a very short time, focus on long-term goals and habits. Learn to eat healthy now and you won't have to reverse these habit in the future when it is much, much harder.