Why calorie counting is inaccurate even if you weigh everything
Precise calorie counting sounds like simple math: weigh the food, check the label, add it up. In reality there are at least three sources of real error in that chain. First, in many countries food labels are legally allowed to be off by up to ±20% and still count as accurate. Second, calorie databases for 'generic' foods (like 'chicken breast') average dozens of different cuts and cooking methods that genuinely differ in calorie content.
Third — and the least obvious — how many calories you actually absorb from the same food varies between people based on gut microbiome composition: some people extract more energy from food than the label suggests, others less. Studies on nuts and whole grains have found calorie-absorption differences of 10–15% between individuals purely from fiber and how it interacts with gut bacteria.
Practical takeaway: calorie counting is a useful tool for tracking a trend, not a precision instrument. If your results after 2–3 weeks don't match expectations, it's more useful to adjust the plan based on the real-world outcome than to hunt for a math error down to the last calorie.