Make it up in the next day or two by eating less until your AVERAGE daily calories are back in line with your goal, IF, you want to stay on goal. Otherwise, you will have to extend your goal date. Keep in mind that it’s not what you do one day but it’s what you average over any period of time that will determine your weight/fat change. For example, if you need to eat an average of 2,000 calories/day to lose 1LB/wk, you can eat 3,000 one day and 1,500 for the next 2 days so your average calorie intake during that time period is still 2,000/day. This will keep you on track towards your goal.
Since there are 3,500 calories in 1 pound of fat, if you extend out the above example for 4-weeks in order to lose ~4LBS, you need to burn 14,000 calories more than you eat for the MONTH. (4 lbs X 3,500 calories per pound =14,000 calories) Again, it doesn’t matter how you accomplish this but you certainly want to make it easier by spreading it out as evenly as possible during the month.
In summary, when it comes to strictly weight management, it’s not WHEN or WHAT you eat and do, but HOW MUCH you eat and move over any GIVEN TIMEFRAME. Your weekly mass changes (overall trend), measured by weight and/or body fat, validates whether or not you accomplished your deficit goal.
Final Note: one single fact determines the rate of weight/fat loss: the average daily calorie deficit. This is defined as the difference between how many calories you burn and how many calories you consume over a given period of time. Weight loss should proceed at a pace that does not compromise health or performance.