You can get a "Resting Metabolic Rate Test" that takes 15 minutes. That will tell you the base calories you need to maintain current body weight by measuring th

You can get a "Resting Metabolic Rate Test" that takes 15 minutes. That will tell you the base calories you need to maintain current body weight by measuring the amount of oxygen your body burns while breathing. I think I paid less than $100 for this. You can also get a Dexta scan that tells you your body body composition, how much fat, how much muscle mass. I think I pay $70 every scan and get one a couple of times a year. You can use this data also to calculate estimated required calories, body composition, are you loosing fat/muscle and gives data to change diet accordingly. You only need to be in a small 300 cal deficit to loose weight. If you want to maintain muscle mass and drop body fat it's better to be in the smallest deficit possible and this will also reduce hunger. If you want to loose body weight quickly and maintain muscle that's hard! That does require a bigger calorie deficit by reducing food, and increasing activity (cardio) to burn more while getting macros exactly right to hold on to as much muscle as possible although you will loose muscle. Bodybuilders are experts at this, they pile on weight during the off season so they are in a calorie surplus so they can gain muscle then diet down to single digit body fat percentages trying to hold as much muscle as possible. Everyone talks about loosing weight but you can not weigh much and be fat aka skinny fat and unfit. Alot of 'slim' people will fit in to this category unless they have an active lifestyle. The modern normalized diet is terrible. It's carb / sugar heavy. There's nothing wrong with carbs you need them but people are eating far to many of them while not burning them and everything is sugar heavy which your body naturally wants to eat more of. My girlfriend has mental health issues and over the past few years has become morbidly obese which causes bigger and bigger issues as I eat my veg, carbs, protein mainly whole foods. I weigh the quantities, look good, in great health medically etc. I eat well, 3500+cal a day as I burn it off with lifting weights and doing cardio. On the other end she eats complete rubbish, sugary comfort foods, lots of fruit as it's good (high sugar), lots of full fat milk as it's good, lot's of olive oil as it's good for you, and now morbidly obese and still gaining, high cholesterol, deteriorating mental health yet somehow I'm the one with the eating issue as I watch what I eat as I eat mainly for performance, going to the gym after work most evenings isn't normal and shouldn't have to do it. She wants to loose weight but doesn't want to put in the work, she sees the stuff she's eating as normal, doesn't want to sacrifice them and sees going to the gym as abnormal. She's right the gym is abnormal in the sense it's replacing the active activity we used to do before sedate lifestyles but it's not abnormal to make your body exercise it in a way no longer doing sat at desks all day.