If you could give one piece of fitness advice or a training tip

Don’t bother What would it be?

Just eat a lot of ECA. You don’t get hungry anymore. 
 

Also everyone partial to a slice of cake, but not enough to sticking a couple of fingers down your throat.

Do a few different sports/activities.  Breaks it down mentally, helps me at least.

e.g. Tennis each Monday, football each Tuesday, etc... is an easier commitment than running for an hour every day and never shaking it up.  

 

I guess  you get a lot of exercise walking from one pharmacy to the next to collect enough ephedrine, eh 

Listen to your body: if you are ill, injured or even just don't feel like it, have some time off and get back on it, but don't quit.

So whatever it is that keeps you doing it. Consistency is more important than the type of activity. 
 

having said that, some activities are more efficient than others and it’s also important to push yourself. 

"So whatever it is that keeps you doing it. Consistency is more important than the type of activity. "

This, unless you want to get strong and ripped, in which case it's all about lifting 

As well as sports/gym etc build something built into your day like cycling to work or running everywhere rather than walking. 

Sports rather than gym.
 

By all means do some functional fitness type exercises, but don’t become one of those  ‘max rep’ lifty gym people. 

Depends what you're looking to achieve but basically find something you like doing and do it a lot. Also have a target. 

Of course squats don't damage your knees. Not unless you do them with crap form. 

 

Mine would be: have a plan. Don't aimlessly go in and do stuff in the gym or with running (or even blindly follow the plan a 23 year old trainer who took a weekend course writes out for you). Be clear on what you want to achieve - what's your end goal, and train specifically towards that. You need to think about what you want to work on (strength, flexibility/mobility, cardio? What balance between those things?) and figure out a plan for that. 

Walk up stairs rather than use the escalator or lift.Get off the tube a stop early and walk the rest. 

I’ve got a few (breaking the rule I know):

Stay mobile at work. 
Consistency is better than heroism. 
Enjoy it. 
Mix it up. 
Ignore fads - you need both cardio and weights. 
You really don’t need all those carbs. 
Ditch the gym - save time and money and avoid germs. 
Buy nice kit - no one wants to dress like a bag lady. 
Explore the gamification of exercise - Zwift etc. What tech is doing there is incredible. 
Indulge in tech. That bike computer is pricey but almost certainly worth it. 

Trite and not always true but good rule of thumb when running in the early AM is "first step out of the door is the hardest".

Putting on the running gear as soon as you get out of bed also helps.

Always viewed food as nothing more or less than fuel. Eat anything that doesn't make you feel disgusting or vomit afterwards. Never had to lose weight but I can't imagine one could get fat by eating bland food 80% of the time.

Fatties tend to be the pickiest eaters.

It's 50% gym 50% what you eat.  

You can train like a muthafooker but if you are on Uber Eats or at KFC every night you will only get limited results.

At the simplest of all levels - work out how many calories you burn every day, to include your gym time, and try not to exceed that in food intake.  It really is that basic.  You don't need a fancy diet from a PT or nutritionist.  

The trick is to feel full in order to avoid over eating at meal times. 

Stay away from crisps and sweets.  Drink lots of water.  

Snack with fruit or smoothies (Puriton made in a blender with skimmed milk is particularly good - and they have some awesome flavours).  

The biggest immediate change you can make is to limit your alcohol intake and switch from beer to clean spirits (Vodka, Gin) or if you can't stomach that try wine.

If you struggle to find the motivation to exercise order a decent high caffeine pre-workout and mix with water.  20 minutes later you will be buzzing and ready to go.  

The best time to exercise is right now. There is always an excuse not to, but ignore that impulse. Otherwise you end up dribbling along averaging 1.7 runs a week or whatever which just isn't enough to get fitter.

- build movement into your day, either walking or cycling. Driving a car every time you leave your house is catastrophic.

-  go for at least 1 or 2 runs a week, always, forever. Doesn't matter how long or how quick, just make sure you do it regularly.

- work out your muscles at least once or twice a week, always, forever. Doesn't matter how much weight or where you do it, just do it regularly. Regular press ups/pull ups at home are great if you don't fancy the gym.

- keep your weight stable and healthy, otherwise forget about it.

- entirely avoid processed foods and drink only water, tea, coffee and alcoholic drinks.

- as you get older it becomes more important to listen to your body, stretch, see a sports masseur or physio as soon as you pick up any niggle.

You can't lose fat unless you sort out your diet.  You can be fitter, or you can also build muscle, but you won't get rid of the fat.  As someone else said, diet is (at least) 50% of it.  

I've done different things at different times, sometimes more cardio (mainly running) and sometimes more body weight stuff and sometimes more weight training.  A balance is best, or you end being lean, with no muscle mass, or have muscle mass, but would fall over wheezing if you ran 100m.

If you can't train 3 times a week, make sure you do it once - you can have a lighter week and pick it up.  It's far better than doing nothing.

Having tried it, I'm now massively against smoothies etc - sugar, including fructose is actually really bad.  You need to be having 5 (or 10 preferably) portions of fruit and veg a day, but actually that should probably be 80/20 veg over fruit.  I had a period with a big breakfast smoothie every day and it completely screwed with my digestion and made training and body weight far harder to manage. 

Cut down on sugar, particularly the refined stuff, and if you can cook everything you can from scratch, that massively helps.  But also don't go the other way - having some chips, or a pizza, or a few beers is fine, just balance it out.  Also, don't kid yourself that eating something "low fat", or from a healthy range, if it's processed food / a ready meal etc means you have a good diet - it's garbage.  Far better to have some chips every now and again than eat that crap.