Presently have six Greenwing Macaw (17 yo), Red Fronted Macaw (12 yo), Red Lored Amazon (17 y.o.), Lilac Crowned Amazon (about 43 y.o.) and a Congo African Grey (11 y.o.)
Panama Amazon (1 Y.O.)
An average weight for a male Senegal is about 156 grams where as a female is in the 130's. Some females can be leaner like mine she is about 127-129 grams. Mine rarely over eats. In fact I think my parrotlet eats more than my Senegal. She is always munching on something, whereas my Senegal eats only when she's really in the mood or if I have something she has to try. My parrotlet hates trying new foods so she leaves me alone about it. Haha. But she is a real porker. If you are really concerned get a digital scale, it's always good to have one and weigh him. I got my from Walmart and it converts to grams which is what you want.
P.S. yours is still a juvenile so don't freak out if his weight is not 156 grams. He's a young fellow. If he is over that then you may want to reconsider what you are feeling him. What are you feeding him?