Can you remember what you ate yesterday? If asked, most people will be able to give a vague description of their main meals: breakfast, lunch, dinner. But can you be sure you've noted every snack bar in your car, or every handful of nuts at your desk? Most people will have a feeling that they've missed something out.

We originally had this suspicion back in 2016, puzzled by the fact that national statistics showed calorie consumption falling dramatically over past decades. We found reliable evidence that people were drastically under-reporting what they ate.

Now the O?ce for National Statistics has confirmed that we are consuming 50% more calories than our national statistics claim.

Why is this happening? We can point to at least three potential causes. One is the rise in obesity levels itself.There is good evidence that under-reporting rates are much higher for obese people. The main reason for this seems to be that obese people simply consume more food, and thus have more to remember.

Another cause is that the proportion of people who are trying to lose weight has been increasing over time. People who want to lose weight are around 10 percentage points more likely to under-report their eating-regardless of whether they are overweight or not. This may be driven partly by self-deception or “wishful thinking”.

The final potential cause is an increase in snacking and eating out over recent decades — both in terms of how often they happen and how much they contribute to our overall energy intake. Again, there is evidence that food consumed out of the home is one of the most poorly recorded categories in surveys.

So, what's the message conveyed? For statistics, we should invest in more accurate measurement options. For policy, we need to focus on options that make it easy for people to eat fewer calories. If people do not know how much they are eating, it can be really hard for them to stick to a diet. Also, we should be looking for new ways to ensure what they eat wouldn't have much impact on their waistlines. If this works, it won't matter if they can't remember what they ate yesterday.