Start living simply. Do not have material possessions beyond your basic requirements which keeps you safe and healthy. Few tips for this are as follows.
Stay near your office/workplace. This helps on multiple fronts. It saves time for commute. It saves money on commute. You can buy a small bike, bicycle or even walk till the office like me. Last 2 options would also be good enough to complete your 50% of quota for physical exercise.
Do not compromise on basic things for saving money. It's not worth it. You'll end up in trouble by spending more on health and medical expenses.
Eat homemade healthy food. Do not eat outside unless absolutely necessary.
Have good Health and Life insurance. Check your company healthcare policy and insurance. You also must have the company doctor or dispensary. Use these things for maximum benefit.
Use the gym at office. It would save money for separate gym. If your office does not have gym or if it's too crowded then or you're shy to exercise in presence of many people then you can practice Yoga like I practice in privacy of your home. All it takes is free space of 4x6, a cotton mattress and willpower. It will minimize your medical expenses.
Buy an electronic UV water filter if needed. Will cost you hardly 100$. It will help you to minimize the cost and pain due to waterborne diseases. Do not buy an RO type water filter unless you're getting water which contains heavy metals like copper, arsenic and zinc in large quantity. Normal hard groundwater is safe for human consumption unless any mine, chemical or fertilizer plant is in close vicinity. And groundwater rich in calcium and potassium can actually serve as dietary supplement.
Have very basic things at home. TV is overrated. Don't buy a TV. You'll be bombarded upon by adverts and it would provoke you to buy more. You'll also be compelled to buy cable which is bad for your pocket and health.
De-clutter your home/ Living space. Don't have any decorations. More stuff you have more time you spend on taking care of the stuff than tking care of yourself.
These are all the lifestyle changes in personal life which are very private and people at your workplace are unlikely to know about it. Now few obvious and visible things I would advice, you might get a lot of heat from peers, friends and family members for this.
Let's start with a bit less obvious things. When you are out at a party, eat in moderation. Stick to simple, healthy and easy to digest stuff. Most of the cases of food poisoning and sickness result from mass prepared food at eateries and canteens as well as parties.
I would say same thing for eggs and meat. I am complete vegetarian for religious purpose and it actually makes sense here due to relatively warmer climate. Also Non veg food is very costly as it is costly to raise animals and devote the feed for them as you can feed 2 times more people with corn or wheat. But I really cannot comment about this as if you're in Europe then it might be difficult to maintain health without having non vegetarian food.
I would say smoking and the drugs are absolutely unnecessary things to be addicted to. I am not gonna try to convince you for this.
If you live simple life like this, you would never run into any financial trouble. However, I cannot guarantee you that you would not run in "ANY" trouble. The most obvious trouble you would be running into is social trouble. We're living in an era of he consumerism. You would be judged from not only how much you earn, but how much you show you spend. That's it's become the prestige thing to suffer from lifestyle related diseases like Diabetes, High BP and other cardiovascular ailments. If you live like I mentioned above, people would make fun at you and you would be excluded from social events because of your frugal lifestyle, people would not care if you are can afford to live exorbitantly. They'll just see if you spend like them. So to live life this you need to have powerful allies with you. You can enlist and confide people very close to you. If you are not financially dependent on anyone then it would be a great thing.
Talk it out with your spouse/ live in partner/ bf or gf. (S)he would prove to be most important ally/enemy in this battle against crazy consumerism. If your views on finances and spending do not match then cancel your plans for frugal living or be ready for the heartbreak. I would choose the later and before marriage I discussed and talked to my fiancee about it directly stating my choice directly to her. If you are not in a committed relationship, check with your would be partner as this is the biggest thing in relationship break up.
Talk to people who are close to you after your spouse. They would probably include your siblings and adult kids. If the kids are very small then you're kind of helpless as they would be bombarding you with their nagging and they would probably want the same toy as their friends/ Be ready for that. Adults should be understanding, but if they berate/ belittle you, do not get discouraged. Stick to your plan.
Stay away from the people who are financial liability due to their way of spending. I know of many people who buy a big TV or XBox One but do not get the health or term insurance for themselves and rely of social connections for emergency funds. I also know of people who spend without thinking of tomorrow and beg people for money when times are bad. These people are liabilities. Better to stay away from them and maintain a respectable distance from them.
You cannot curb the office gossips and general talks people do about you in the social circles. But as the time would progress, you would notice that you would be much happier than the way you're living now. People would admire you in secrecy and would try to do the stuff like you but will not say these things to you directly. Few years down the line you can also coach people with their finances and frugal living. And if you are master of words then you can become a new age spiritual leader.