We analyzed one assertion on whether a high-protein breakfast reduces lunchtime calorie intake, and the evidence we’ve reviewed so far leans toward a reduction. In this study, participants who ate a breakfast with 20 grams of protein from high-protein instant ramen consumed, on average, 94 fewer calories at lunch compared to those who ate a breakfast with only 6 grams of protein [1]. Importantly, this change happened even though participants reported similar levels of hunger and fullness before lunch, suggesting the effect may not be driven by subjective feelings of appetite [1]. We did not find any studies that contradicted this finding, but the total number of assertions reviewed remains very small — only one. This means our current analysis is limited in scope and does not reflect the full range of possible meals, protein sources, or populations. The study used a specific food — instant ramen — and it’s unclear whether the same result would appear with eggs, Greek yogurt, tofu, or other protein-rich foods. It also doesn’t tell us whether this effect lasts beyond one meal or over days and weeks. What we’ve found so far suggests that increasing protein at breakfast, at least in this specific form, may lead to lower calorie intake at the next meal — even without people feeling noticeably less hungry. But because we’ve only reviewed one assertion, we can’t say whether this pattern holds more broadly. More research with different foods, longer timeframes, and diverse groups is needed to understand how consistent this effect might be. For now, if you’re looking to eat less at lunch, swapping a low-protein breakfast for one with around 20 grams of protein — even from a convenient source like high-protein ramen — might help, without needing to feel fuller beforehand.