WASHINGTON — American consumers borrowed more heavily in July, increasing their debt primarily in a category that includes auto and student loans.

The Federal Reserve said Friday that overall consumer credit rose $18.5 billion in July, up from the $11.9 billion increase in June.

Economists and financial markets watch the credit report closely for clues about the direction of consumer spending, which accounts for about 70 percent of economic activity.

Nonrevolving credit, which includes auto and student loans, increased $15.8 billion. The category that includes credit cards advanced $2.6 billion.

The July increase brought consumer credit to a total of $3.75 trillion. The Fed’s monthly credit report does not include mortgages or other debt secured by real estate, including home-equity loans.

Increased loan demand is often a sign of continued economic growth.