Get all custom fields with wp's get_posts()

Question

This is for a JSON API Endpoint (not a web site). Currently I'm getting all custom fields for a post separately via

get_fields($post_id)

Is there any way to get all associated custom fields with the get_post / get_posts functions?

How I'm merging now:

    try {
        // gather all the posts
        $posts = get_posts(array(
            'posts_per_page'    => 20,
            'orderby'           => 'date',
            'order'             => 'DESC',
            'post_type'         => 'custom_post',
            'post_status'       => 'publish'
        ));
    } catch(Exception $e) {
        return $this->error($e->getMessage());
    }

    try {
        // merge the acf in with the original post data
        for($i = 0; $i < count($posts); ++$i) {
            $post = $posts[$i];

            $acf = get_fields($post->ID);

            $post->acf = $acf;
        }
    } catch(Exception $e) {
        return $this->error($e->getMessage());
    }