Dress for extreme temperatures
Your end goal should not be to reduce weight, but to reduce mission costs, and a lack of clothing actually increases your mission costs despite reducing weight.
Depending on where you are, space is generally going to be 1 of 2 things, it is either really hot or really cold. In the deep of space, your ship needs an Active Thermal Control System which could require several kilowatts of continuous power per crew member just to keep your living area in a habitable temperature range. While clothing tends to be light weight, power and environmental systems are very heavy. So keeping your crew area comfortable for naked people is actually more expensive than clothing them and keeping your cabin a bit hotter or colder.
If you are in a hot area of space, you can put on a hot suit which assists with your natural perspiration to help your "sweat better" keeping you cooler than if you were naked. Or if you are in cold space, a cold suit can insulate you making you warmer. With well thought out clothing designs, a few hundred grams of synthetic fiber can allow you to keep the cabin at a good +5 to -20°C outside of comfortable ranges for a naked crew which could easily save you several kg and thousands of dollars worth of solar/reactor/HVAC equipment per crewman.
So, if you want to cut costs by cutting a couple of kg from your mission weight, it is better to cut back a bit on your Power and ATC systems knowing that this might cause the occasional brown out, and give your crews the clothing they need so that when someone runs the coffee maker and the microwave at the same time, it doesn't lead to everyone freezing their ###s off.
There is also the liability issue of sending a mostly naked crew into space. While you might save a few hundred dollars per naked crew member, if a sexual crime of any nature takes place during the mission, you risk a lawsuit for creating a working environment that may have encouraged that crime to happen. So, your mission command organization could realistically get sued for millions of dollars for creating an unsafe workspace. Even if you can't prove that there is a single practical advantage to clothing in space, your legal department would never allow such a minor cost cutting practice.
These factors together mean that the ideal space attire is actually going to look a lot more like a Star Trek Federation uniform than a space bimbo bikini.