begin{frame}
frametitle{Size changed}
scalebox{0.8}{begin{minipage}{1.20textwidth}

... your content here ...

end{minipage}}
end{frame}

begin{itemize}
item First item.
  begin{itemize}
  item First subitem.
    begin{itemize}
    item lipsum[75]
    item lipsum[66]
    item lipsum[75]
    end{itemize}
  item Second subitem.
  end{itemize}
item Second item.
item Third item.
end{itemize}

begin{frame} {Scale Items}
makebox[1.1linewidth][c]{scalebox{0.8}{begin{minipage}{0.8linewidth}
begin{tabular}{l | c | c | c | c }
      & Column1 & Column2 & Column3 & Column4 \
hline hline
Line1 & Value11 & Value12 & Value13 & Value14\
Line2 & Value21 & Value22 & Value23 & Value24\
Line3 & Value31 & Value32 & Value33 & Value34\
Line4 & Value41 & Value42 & Value34 & Value44
end{tabular}
end{minipage}}}
end{frame}