Breakfast is the most important meal of the day.

Analysis

The phrase was popularised by cereal manufacturers in the 1910s–1940s and entered public health messaging in the mid-20th century.

Observational studies repeatedly find breakfast eaters have lower BMI and better cardiometabolic markers, but these studies cannot separate breakfast from the lifestyle factors that correlate with it (regular schedules, lower smoking rates, more total physical activity).

Randomised trials that explicitly assign people to breakfast or no breakfast generally show no significant weight-loss or weight-gain difference. Effects on cognition in adults are small and inconsistent; effects in children from food-insecure households are larger and more reliable.

The engine returns Contested because the claim's truth depends sharply on the population: 'most important' is well-supported for food-insecure children, weakly supported for the general adult population, and not supported as a universal rule.

Sources Weighed

• American Journal of Clinical Nutrition, Sievert et al. (2019)
  Systematic review of RCTs
  Found no consistent weight-loss benefit from eating breakfast in adults.
• Pediatrics, Adolphus et al. (2013)
  Systematic review
  Stronger and more reliable cognitive effects in undernourished children.
• Kellogg Company advertising archive (1944)
  Primary historical document
  Documents commercial origin of the slogan.