100 kcal is ~0.5 kg of fat per month, or 6 kg per year.
Read that again. Six kilograms, per year. Every year.
Given a person consuming near their total daily energy expenditure, that’s the difference between losing almost 20 kg since the start of COVID, and gaining 20 kg.
Small changes over time compound in unintuitive ways, which is all the more reason not to dismiss them so flippantly.