People are bad at reporting what they eat. That's a problem for dietary research

I have been obese for many years and also now if I do not pay attention to what I eat I gain weight immediately.

Eventually I have learned to control exactly what I eat, in order to control my weight, but I no longer find this difficult, mainly because normally I eat only what I cook myself (with the exception of trips away from home).

When I experiment how to cook something that I have never cooked before, after I reach a stable recipe with which I am content, I measure carefully every ingredient, either with digital kitchen scales or with a set of volumetric spoons. Then I compute the relevant nutrient content, e.g. calories, protein content, fatty acid profile, possibly some vitamin and mineral content, in the cases when there exists a significant content of that.

While I do this carefully the first time and I record the results, whenever I cook the same later I do not need to pay attention to this, because I already know the nutrient content, so summing for all the portions of food that I plan to eat in that day I can easily estimate the daily intake for everything.

The essential change in my habits that enabled me to lose the excessive weight was that in the past I was eating without paying attention to quantity, until I was satiated, while now I always plan what amount of food I will eat during a day and I always cook the food in portions of the size that I intend to eat, which is always the same for a given kind of food, so I no longer have to repeat any of the computations that I have made when I have determined for the first time a recipe.

In a recipe, things like spices can be ignored, because they add negligible nutrients. Even many vegetable parts, like leaves or stalks, or even some of the roots or of the non-sweet non-fatty fruits, may be ignored even when used in relatively great quantities, because their nutrient content is low. So such ingredients may be added while cooking without measuring them.

For many vegetables and fruits, which are added to food as a number of pieces, I do not measure them when cooking, but when buying. I typically buy an amount sufficient for next week, which is weighed during buying. Then I add every day a n approximate fraction of what I have bought, e.g. 1/7 if used for cooking every day. Then for estimating the average daily intake, I divide by 7 what I have bought for the week.

What cannot be ignored and must always be measured during cooking, to be sure that you add the right amount, are any kinds of seeds or nuts or meat or dairy or eggs, anything containing non-negligible amounts of starch or sugar, any kind of fat or oil or protein extracts. Any such ingredients must always be measured by weight or by volume, to be sure that you add the right amount to food.

Nevertheless, measuring the important ingredients adds negligible time to cooking and ensures perfectly reproducible results.

I eat only what I cook myself and I measure carefully everything that matters, but the total time spent daily with measurements is extremely small. I doubt that summing all the times spent with measuring food ingredients during a whole day can give a total of more than one minute or two. Paring and peeling vegetables or washing dishes takes much more time.

or you're sleeping like shit. or you have an autoimmune disease. or you're depressed. or you have an ongoing inflammatory state from a lingering virus. etc

This won't be useful for you because you share food with others, but for people who do not share food and are interested in long term tracking rather than short term (e.g., they want to take off some weight at a healthy rate and keep it off, as opposed to people who just want to lose a few pounds rapidly for their class reunion and will make no effort after that to keep it off) there is a simple trick that can make it a lot easier.

That trick is to focus on months instead of days. Then count your calories when you buy the food instead of when you eat it. For example lets say you buy a loaf of bread. It is 100 calories per slice and there are 17 slices. Add 1700 to your calorie count for the month.

At the end of the month you can approximate your average daily calories as the amount of calories you bought that month divided by the number of days.

Some things you buy in a month might last into the next month. That will introduce some variation but over longer periods it should cancel out. If you want you can smooth that out a bit by logically splitting those items when they have a lot of calories.

For example consider jar of mayonnaise that might last a few months and is 8000 calories. Instead of counting all 8000 in the month you buy it you can count it as 2000 that month and 2000 more each of the next 3 months.

> Yup, it will. Nobody said tracking nutrients was quick.

well, many say it's "easy" (it's not)

I do this with the Xiaomi Mi Scale 2. You can connect it to Home Assistant. Once it has a stable reading, it auto-submits, but there's no button for flagging, although you could potentially build this yourself. I never had to connect the scale to the internet; it just worked with Bluetooth