Calculate the average weight of male athletes from Tonga.
AVG(weight) where region_name = 'Tonga' and gender = 'M';
SELECT AVG(T3.weight) FROM noc_region AS T1 INNER JOIN person_region AS T2 ON T1.id = T2.region_id INNER JOIN person AS T3 ON T2.person_id = T3.id WHERE T1.region_name = 'Tonga' AND T3.gender = 'M'