"Breakfast Is the Most Important Meal": What Randomised Trials Actually Found

A sentence we've heard since childhood, and one on which enormous advertising campaigns were built. So what does the highest tier of evidence say?

What the randomised trials found

A meta-analysis published in the BMJ (Sievert et al., 2019) covering 13 randomised controlled trials found that those who skipped breakfast lost 0.44 kg more than those who ate it, and that the evidence does not support eating breakfast as an effective weight-loss strategy. It also noted that breakfast eaters consumed more total daily calories^[1]. A later meta-analysis in Obesity similarly found no clear adverse effect of breakfast skipping on body composition^[2].

Why did we believe the opposite?

Because older observational studies showed an association between skipping breakfast and weight gain — but breakfast skippers in those studies were also less likely to follow a healthy lifestyle overall^[1]. Correlation is not causation, a lesson that repeats throughout nutrition science.

But careful: this is not an invitation to skip breakfast

The National Weight Control Registry, which tracks thousands of people who have maintained weight loss for years, finds that about 80% eat breakfast daily^[3]. There is no contradiction: breakfast is not a fat-burning trick, but it may be an excellent discipline tool for people who overeat at night.

The practical bottom line

• If you eat breakfast, feel full and stay consistent: carry on, you're on the right track.
• If you have no appetite in the morning: don't force it, and don't feel guilty — the evidence is on your side.
• The only constant rule: your daily total determines the outcome, not meal timing.