That 25% difference is for a single serving of food and only translates into a ~2.5% error in your daily food total. People eat a varied enough diet that a 25%

That 25% difference is for a single serving of food and only translates into a ~2.5% error in your daily food total. People eat a varied enough diet that a 25% difference in a single food item really won't make a huge difference. Lets take a man who needs ~2500kCal per day to maintain his current weight. A nice steady loss of 1lb per week would require this guy to eat at roughly a 500kCal/day deficit (a total deficit of 3500kCal translates to a fat loss of 1 lb). Even underestimating his total caloric intake by 10% (he eats 2200kCal instead of 2000kCal) every single day will still see him losing weight at .6lb per week. After 4 weeks of this he can see that he's only lost 2.4 lbs and can therefore reduce his intake by another 200kCal/day to achieve the desired 1lb/week loss. Tracking your weight/calories like this makes it fairly trivial to lose weight. It really doesn't matter if all the individual food items have perfectly assessed caloric content...as I say, they're close enough.