Hi Caroline, Welcome to the forum.
I have a fairly physically active lifestyle, not from the gym but rather from my work. I have spent time with NHS nutritionalists who were unable to help me lose weight. – But I have been successful so far with this WoE, I have reached my initial target weight and plan to continue on to loose another one or two dress sizes.
Its not calories you eat that is important, its the macros (carbs / protein and fat) and the impact those have on our hormones. Our bodies do not have any method of monitoring the number of calories we eat. – The hormone regulation which controls if we put on weight, or turn to our own fat stores for fuel is driven by insulin levels. – If you keep your carb intake low and protein levels moderate so you have low levels of insulin then your body can access your own fat stores to make up the difference between the calories you eat and those you burn. – This is called ketosis, If your insulin levels are high then your body can’t access your fat stores and instead has to become more efficient in how many calories it needs to function.
If you go through the Take a look at this thread you will find quite a few links to articles and podcasts by people like Dr Bikman, and Dr Fung which help to explain this in more detail.
Depending on what your ratio of carbs / protein and fat looks like at present, you may want to take it in stages. Cutting out the “big whites” as I call them, bread, potatoes, rice, pasta, flour etc and then once you are used to that bringing your levels of carbs down more until you are in fat burning mode. The level of carbs you can tolerate and be in fat burning mode varies for different people, some can cope with 50g a day, others have to get below 20g.
You may struggle initially with energy levels when you change over to low carb simply because your body is out of practice. However, I recently discovered that “carb flu” is linked to an electrolyte imbalance, so adding salt to your diet reduces the problems. – There is a link to an article on this also on the take a look at this thread.
You may find the book the Art and Science of Low Carb living by Dr Phinney as well as podcasts he has published as a useful resource. He is very focused on low carb for sports people.