"There may be a misconception in adolescent medicine ...that it 'takes a couple of years after menarche to get the engine running' and hence one might not want to be concerned about irregular adolescent menstrual cycles until much later," said Charles Glueck, one of the study's authors.
"That's clearly wrong," he added, noting that even in young teenagers, very irregular menstrual cycles are not normal and should not be ignored.
Glueck and his colleagues followed 370 girls, starting at age 14, as part of a study.
Once every year, girls were asked how long it had been since their last menstrual cycle.
Researchers also periodically measured their levels of different sex hormones, glucose and insulin, and blood pressure.
They also collected information on girls' height, weight and waist circumference.
Between age 14 and 19, 269 of the girls reported regular periods at every annual visit.
Another 74 of them had only one report of an irregular period, 19 girls had two reports, and eight said it had been at least 42 days since their last period at three or more visits.
The girls with the most reports of irregular periods were already heavier than others at age 14, and gained more weight and inches on their waist during the study. They also had higher levels of testosterone.
Reports of irregular periods were also linked to higher levels of blood sugar and insulin at age 25.
The findings do not prove that irregular periods cause girls to gain weight or are responsible for the increases in glucose and insulin levels rather, the irregularity could signal another problem.
Irregular periods might be a sign of polycystic ovary syndrome, or PCOS, which can cause fertility problems, Glueck said. But catching it in adolescence means it can be "very successfully treated."
Does your teen have irregular periods?