Answering in the first sentence generally helps and almost never hurts. Leading with the answer satisfies the searcher immediately and builds trust, and the depth below still earns continued reading from the people who want it. The common fear, that giving the answer away upfront makes everyone bounce and tanks your dwell time, is mostly unfounded when real depth follows the answer. People who only needed the quick fact were going to leave the moment they got it regardless; people who want the full picture stay for the part you put underneath.
The trust effect is the underrated half. When a visitor lands and finds the answer right away, the page feels credible and respectful of their time, which makes them more willing to keep reading your explanation, your caveats, and your detail. Hide the answer and you create friction instead: the reader scans, gets impatient, and often leaves to find a page that just tells them. So the move meant to hold attention frequently does the opposite, and the move people fear, answering first, is what actually keeps the willing reader engaged.
It’s also worth being honest that dwell time isn’t a confirmed ranking factor in the way the worry assumes. Google has never clearly established time-on-page as a direct signal, and how it interprets user behavior is debated and not transparent. Treat dwell-time claims as an unconfirmed signal worth verifying rather than a target to optimize for. Optimizing your content structure to game a metric that may not exist, at the cost of a worse experience for real readers, is a poor trade even before you consider that it tends to backfire.
So lead with the answer and offer depth below it. Don’t withhold the answer to manufacture longer sessions, and don’t build your page around dwell time as if it were a proven lever. State the answer in the first sentence, then give the explanation, examples, and nuance that reward the reader who chooses to stay, and let the metric follow from genuine usefulness rather than the other way around.