Do Dads Determine Height and Moms Weight? The Genetics Myth

You've probably heard someone say it at a family gathering: "She got her height from her dad and her weight from her mom." It sounds scientific enough that people repeat it confidently. There's just one problem—it's not how genetics actually works.

This persistent myth oversimplifies the fascinatingly complex way our bodies inherit traits. The truth involves thousands of genes, environmental factors, and a whole lot of genetic shuffling that can't be reduced to "this from dad, that from mom."

What the Research Actually Shows

Scientists estimate that about 80-90% of height variation is determined by genetic factors, but those genes come from both parents in roughly equal measure. Recent genome-wide studies analyzing millions of people have identified over 12,000 genetic variants that influence height—and you inherit a random mix from both your mother and father.

There's zero scientific evidence that height genes predominantly come from fathers. Each parent contributes approximately 50% of the genetic blueprint for your stature. That's why you can inherit your grandmother's petite frame even if your dad is tall, or why siblings from the same parents can have noticeably different heights despite identical parentage.

The Weight Question Gets Messier

Weight and body mass index show even less parental specialization. BMI heritability sits around 39%—notably lower than height—meaning environmental and lifestyle factors play a much bigger role.

Here's where things get interesting: mothers do have slightly more influence on a baby's birthweight specifically, but not because of genetic dominance. The developing fetus grows in the mother's body, directly affected by her nutrition, health conditions, and prenatal environment. That's environmental influence, not genetic programming.

Once a child is born and growing, both parents contribute equally to genetic weight predisposition through that same complex polygenic inheritance pattern. If both parents have obesity at age 17, research shows their child has about a 77% probability of having obesity at the same age, compared to just 15% when both parents are in a healthy weight range.

Why This Myth Persists

The "height from dad, weight from mom" idea probably survives because:

• People notice patterns in individual families and generalize them
• It provides a simple explanation for complex biology
• Confirmation bias—we remember when it seems true, forget when it doesn't
• It gets repeated by well-meaning relatives who heard it from their relatives

But anecdotes aren't evidence. Your tall uncle might have tall sons, but that's because height genes from both parents happened to combine favorably—not because he transmitted some special paternal height formula.

The Real Story: Polygenic Inheritance

Both height and weight are polygenic traits, determined by hundreds or thousands of gene variants working together. You inherit random combinations from each parent, which is why siblings can look so different despite sharing the same genetic pool.

Think of it like shuffling two decks of cards together. Your parents each hand you half a deck, but which specific cards you get is random. That's why predicting a child's exact height or body type remains difficult even with both parents' genetic information—there are simply too many variables in play.

So next time someone confidently declares that fathers determine height and mothers determine weight, you can set the record straight: genetics doesn't pick favorites, and both your parents are equally responsible for the height you complain about or the metabolism you wish worked differently.