1select sum(s0.w - s1.w) as total_weight_loss
2from (select idMember, max(weight) as w from Measurements m
3 where m.date = (select min(date) from Measurements n
4 where m.idMember = n.idMember)
5 group by idMember) s0
6join (select idMember, min(weight) as w from Measurements m
7 where m.date = (select max(date) from Measurements n
8 where m.idMember = n.idMember)
9 group by idMember) s1
10on s0.idMember = s1.idMember
11