Here is a way to get a (very) rough estimate of the amount of calories you are burning in a day. This is for people who have been weight stable for at least a year. If you are currently at a steady weight, write down everything (remember the Micky Mantra - every bite, lick and taste) you ate yesterday and the day before. Write down everything for today and do the same thing tomorrow. That should give you four days to average. Do NOT change your normal behavior - this includes eating out. If you usually eat out, then you need to capture those meals in your average.
There are many tools available on line (and perhaps in print) that can help you determine the calorie amounts for all of the foods on your list, if you have the serving sizes. [You might have to go four days forward instead of two days backwards for accuracy. The reason I suggested that you start with past days (even though you may forget something) is so you won't change your pattern because you are thinking about it.]
If you purchase foods away from home, you can usually get calorie information from the restaurant's website, but it may be slightly or largely inaccurate. If you prepare your own meals, you can get info on the ingredients from the USDA website. When you feel pretty confident that you have the four days individual totals, add them together, divide by four and that is your average. Remember this is only going to work if you are tracking what you normally eat.
If you are stable, the number you came up with should be the same number that you burn. TEI total energy intake = TEE total energy expenditure in weight stable people.
I will tell you that this type of estimate is closer than any you can get by trying to track your energy burn, outside of a clinical, laboratory setting. The machines at your gym are NOT accurate. Your GPS systems and sports watches are not either (but they are a good measure of consistency and changes - in other words they are reliable even if they are not valid)
I want to be very clear that what I just told you is offered as a way for you to assess in general terms, the amount of energy you use in a day. It is not meant to suggest how many calories you need to maintain or lose weight. The only qualified nutrition guidance that applies to individuals is provided by licensed/registered dieticians. Remember that even if you forget everything else you read. Your personal trainer at the gym is NOT qualified to give you diet advice, unless of course, he or she is an RD.
Nutritional science continues to grow and to challenge our assumptions about food and weight. We are learning that a calorie is not a calorie. What you eat can have an impact on your metabolic processes. Again, that is a discussion to have with a nutrition expert.
Ah, but let me get back to the conversation started with the Lowe article. We will use me as an example. I am very confident that my calorie intake varies from 1600 to 1680 calories a day (higher if I am running more). This keeps me, a very active person who is short and thin, at a stable weight. If I shift that range by even 70 calories, to between 1750 and 1830 a day, I will gain several pounds in a year. Seems like nothing, but of course, we have shifted our normal calorie intake by as many as 300 calories a day and gained many pounds. This can be reversed, in general and at the population level, by a 500 calorie reduction (some say). Sounds like a lot, but if you are one of the people eating 3000 calories a day and switch to low energy dense foods, its a piece of ......... its not that hard.