Could your height be determined (at least in part) by your grandma’s weight? That’s the startling implication of a new study published in the November issue of the journal Endocrinology. The study showed that mothers who were fed a high-fat diet had taller children, and that those children—both sons and daughters—can pass along this trait to their own progeny. If both parents' mothers are heavy, the offspring will be even taller.

But before you conclude that this is the secret to raising your own basketball team, there are some caveats.

First of all, the research conducted by the University of Pennsylvania’s Tracy Bale, associate professor of neuroscience, and graduate student Gregory Dunn was performed on mice, not humans. Dunn and Bale began with nearly 200 normal-size mice. For four weeks, they fed a high-fat diet to one group of adult females and a typical low-fat diet to the rest. They were then bred with normal-size males and continued on their particular diet for the duration of the pregnancy and the nursing period.

Not surprisingly, the females fed the high-fat diet quickly gained weight and had higher blood glucose and insulin levels than the control group. The offspring of the high-fat moms turned out to be heavier than those born to the moms fed the normal diet, but it wasn’t because they were fatter. Instead, they turned out to be 10 to 15 percent longer than the other offspring. After feeding both groups of the offspring a normal diet, Bale and Dunn bred them together, noting which couplings included a female or male offspring of a high-fat mom and which consisted of two offspring of the heavier moms. The second generation of the high-fat moms were longer than the descendants of the normal-diet moms, and surprisingly, this trait persisted through both the maternal and paternal lines. 

While Bale thinks the chances are high that human studies will show the same thing (“It would shock me if it didn’t”), those studies have not yet been done. Bale also says that researchers don’t know yet whether the trait will persist beyond the second generation. Studies to determine that are currently underway.

Secondly, a lot of factors influence height. Heredity, diet, exercise, living conditions, and general health all have an effect on height, and some have an effect on each other. For instance, without an adequately healthy diet, children may never realize the height they were genetically programmed to achieve, and children of shorter parents with poor nutrition can grow to be much taller than those parents if given access to proper nutrition.

Finally, this type of height advantage comes at a high health cost. In the study, the first- and second-generation offspring of the mice moms fed a high-fat diet had greater body length, but they also had reduced insulin sensitivity, which means they were at higher risk of developing diabetes, high cholesterol, heart disease, and obesity. “The disease risks far outweigh the benefits of being taller,” Bale said.

From a scientific point of view what makes this study particularly interesting is that it “shows how maternal and paternal lineages can pass (altered) genes on.” Scientists have known for a while that various environmental exposures (nutrition, stress, etc.) during pregnancy and infancy can alter the programming of inherited genes in future generations, a process known as “epigenetics." For instance, while many studies have implicated the behavior of moms-to-be in creating problems like the current childhood obesity epidemic, fathers’ impact has been much less clear.

The study also gives us one more reason why human height has increased so much in the past 150 years. Over the past century-plus, says Bale, “food has not only become more available, it has become more fat ladened, and we’ve seen heights escalate as a result.”