It can be easy to overeat at work. Your colleagues bring in treats every day because it's always someone's birthday or leaving party. There's a culture that people eat muffins or doughnuts every Friday or even every day. The staff restaurant is full of fried food or mayonnaise laden salads and the nearest place outside work serves nothing but fast food.

Here are 8 tips to immunise yourself against unwanted workplace calories.

1. Bring your own healthy lunch and snacks

You know it makes sense. If you have something healthy and delicious to eat you'll be less tempted by all the other unhealthy stuff around. It takes a bit of planning when you do your weekly shop but you'll reap the rewards. Choose food which is easy to prepare and get as much as you can ready the night before to avoid last-minute panics in the morning.

2. Say "No" nicely

You can get a lot of pressure from others to sample the snacks they bring in so this one may take some practise but it does get easier after a while. Just say "No thanks not just now" or "No thanks, I'm just about to have an apple" or "No thanks I've just eaten" or simply "No thanks" - no need to explain or apologise.

Saying you're on a diet seems to make some people try and persuade you more forcefully. ("One won't hurt", "Surely you don't need to lose any more weight you'll fade away" etc). Before you know it you're giving in. If you really can't stand the pressure say "Thanks I'll save it for later", take it home and throw it out.

3. Keep your desk clear of food

It's asking for trouble to keep food on your desk. Put the lunch and snacks you brought out of sight so that you have to go and get something from the kitchen or locker room when you're hungry. On the other hand, if the kitchen at your place of work tends to be loaded with treats people have left for sharing, you may be better keeping your food at your desk. But at least keep it out of sight in a cupboard or drawer.

4. Stop to eat

Don't nibble food unconsciously at your desk - it's the easiest way to overeat. Pause in whatever you are doing whenever you decide to eat and take time to really taste the food. If there's somewhere you can go away from your desk to eat then do that, otherwise just stop working on your report or reading your emails for 5 minutes and be fully aware of the food you are eating.

5. Stay away from vending machines

Vending machines tend to be full of unhealthy calorie-laden food. Having your own snacks should help you resist the temptation to treat yourself. But, in any case, keep away from the room with the machines and if you really can't resist, stop bringing any change to work - it's the only way!

6. When you need a break

Don't eat just because you need a break. Instead, take a quick walk or have a glass of water or herbal tea - even coffee is better than eating food you don't need. If you find that there are times you just have to nibble on something make sure you always have plenty of healthy snacks with you. You can nibble quite a bit on carrots sticks, cucumber and celery without doing any damage to your waistline.

7. Team up

If you have a colleague who is also trying to lose weight, join forces and help each other stay on track. It's great to have someone to go for a walk with at lunchtime or to commiserate with when everyone else is wolfing down cakes someone has brought in.

8. Choose wisely

You don't have to turn down social invitations from colleagues to be able to succeed at losing weight so go ahead and join in. But you do have to select what you have to eat and drink carefully when you eat out on a regular basis. Choose the smallest portions you can and get to know the menus at the local restaurants so that you can plan what to eat ahead of time. Even fast food places now have healthier options but remember it's often the extras which are the most fattening - condiments, dressings and sugary or milky drinks can more than double the calories in a meal.