Your BMI, or Body Mass Index, is an indicator of overall body fat and takes into account your weight and height. These women all fall into the healthy BMI range of 18.5 to 24.9.

To calculate your BMI, visit www.core.monash.org/bmi.html.

We asked Dr Brian Morton, vice president of the Australian Medical Association (NSW), to explain why these women are healthy - and what they need to change to stay in good shape.

What comes first: size or health? We want to know how you view your 'healthy' body, so tell us by leaving a comment below.

JESSICA, 29

Height: 174cm
Weight: 56kg
BMI: 18.5 Size: 8-10
Pedometer count*: 6011 (weekdays)

9085 (weekends)

TYPICAL DIET:

Breakfast: Nothing or a piece of fruit.
Lunch: Wholemeal bread sandwich with ham, tomato and cheese, or Thai chicken dish with boiled rice on weekdays. Yum cha (steamed, not fried) or sushi on weekends.
Dinner: Lamb chops with vegetables, or salmon with soba noodles on weekdays. Pizza or Asian dishes on weekends.
Snacks: Low-fat yoghurt, fruit, chocolate, rice crackers, rice cakes with honey.
Drinks (daily): Two litres of water, three cups of black tea with milk and sugar.
Alcohol (weekly): Eight glasses of red wine.
Smoker: No.
My body image: "Sometimes I look at photos of myself and think, 'You need to put on weight', but I've never really made a conscious effort to do anything about it. I've always been thin and think I always will be. I've had strangers accuse me of having an eating disorder, which is insulting because I love food. While I think I'd look better with an extra five kilograms, I'm concerned that if I eat more than I already do, then I'll become overweight, not healthy."
Exercise routine: "I walk to and from the train station every day - which is about a 40-minute round trip. I do a lot of running around on the weekends as I don't often drive, but I don't do any structured exercise."

Eating habits: "I rarely eat breakfast and I know that's bad, but I always try to eat a decent lunch to compensate. I have a home-cooked meal most nights and eat out about three times a week. Basically, I eat whatever I want, but I know when to stop."

OUR EXPERT SAYS:

"There are a few reasons why Jessica is very slim. The nutritional value of her diet is OK, but because she's skipping breakfast, there's a long period of at least 12 hours where she's not taking in any kilojoules. Her body is burning up her fat stores to compensate. Genetics also play a part. And while Jessica might be able to eat what she likes at the moment, it won't always be the case. As we age, our activity slows down and so does our metabolic rate. She needs to establish good habits now, such as eating breakfast and doing more exercise. Studies show that exercise at a slow pace doesn't increase fitness or muscle strength, so she should incorporate a hill or a longer walking route into her daily routine."

ALEX, 22

Height: 165cm
Weight: 66.5kg
BMI: 24.4 Size: 12
Pedometer count: 4496 (weekdays)

11,753 (weekends)

TYPICAL DIET:

Breakfast: Small bowl of porridge with skim milk, or one slice of banana bread and a piece of fruit on weekdays. Chocolate croissant or a slice of banana bread on weekends.
Lunch: Wholemeal roll with grilled chicken, rocket, lettuce, onion and sweet chilli sauce on weekdays. Garden salad or pumpkin, pine nut and ricotta salad on weekends.
Dinner: Homemade pizza on Lebanese bread on weekdays. Steak with peppercorn sauce and small garden salad on weekends.
Snacks: Handful of strawberries, two carrots with salsa dip, 45g packet of Maltesers.
Drinks (daily): One litre of water, one glass of orange juice, one flavoured mineral water or Diet Coke (a couple of times a week).
Alcohol (weekly): Six glasses of white wine.
Smoker: No.
My body image: "I'm happy with my height and I feel I'm in proportion. If I could change anything, I'd like to be more toned - my arms, stomach and legs especially. I wouldn't mind a few centimetres off everywhere, too. At the moment, I'm just scraping into a healthy BMI and my aim is to go down one size to a 10. My sisters are all naturally quite thin - they've got Dad's figure and I've got Mum's."
Exercise routine: "I joined the gym in April last year and I do a 30-minute circuit class three times a week. I've been worried about my health ever since I read that heart disease is the number one killer of women. It made me realise that if I don't look after my body now I might not be so healthy in the future."

Eating habits: "Since I started working out, I've been craving more healthy foods, like fruit and vegies. I won't deprive myself, though. I like going out for dinner and I'll have a few glasses of wine. And, if I feel like chocolate, I'll have a little bit and not feel guilty about it."

OUR EXPERT SAYS:

"Alex is probably the healthiest of the five, yet she has the highest BMI, which suggests her genes are playing a part. Genes determine how your body processes the raw materials it consumes, while your metabolism can be impacted by caffeine and exercise. Alex is only doing half the required steps each day, so perhaps she could change the amount she moves to increase her metabolism. She may also want to watch portion sizes, as larger helpings can cause weight gain."

SAMERA, 23

Height: 150cm
Weight: 49kg
BMI: 21.8 Size: 8-10
Pedometer count:
12,004 (weekdays)

5468 (weekends)

TYPICAL DIET:
Breakfast: An Up&Go breakfast drink on weekdays. Nothing on weekends.
Lunch: Fish burger with chips, or a falafel roll with roast vegetables on weekdays. Two-minute noodles, or a baked potato with sour cream and cheese on weekends.
Dinner: Two grilled chicken patties with salad and bread roll, or grilled fish with potatoes and salad on weekdays. Pizza or fetta cheese on Lebanese bread on weekends.
Snacks: Kellogg's K-time Bars, soya crisps, carrot sticks, two Iced VoVo biscuits.
Drinks (daily): 1.5 litres of water.
Alcohol (weekly): Three Malibus with pineapple juice, four glasses of white wine.
Smoker: No.
My body image: "I wish I was taller - I sometimes have trouble buying tops because my torso is so short. Overall, I like my shape because if I was straight up and down I'd look like a child because of my height. I also like that I have womanly curves."
Exercise routine: "I walk to and from the train station every day, which is about a 60-minute round trip. Every night I do 20 sit-ups to keep my tummy flat. I'm more conscious than ever about exercise because I put on weight a year ago when I went overseas for six months. I was horrified when I came back and none of my old clothes fitted me properly."

Eating habits: "Now that I know I have a tendency to put on weight, I've stopped eating a packet of chips every day. I'll go through little phases where I bring carrot sticks in to work, but I'll also snack on soya crisps or muesli bars. At lunchtime, I try to eat a salad rather than a heavy pasta or fried dish."

OUR EXPERT SAYS:

"A lot of people run on adrenaline and are burning up kilojoules through inconsequential things like walking around the office- I suspect this is what keeps Samera slim, based on her pedometer reading. Samera is doing well with the amount of protein she eats, but she is letting herself down with high-fat snacks. The Up&Go she drinks for breakfast is also high in fat and should be an occasional, not everyday, part of her diet. To prevent serious illness in her later years, Samera should start adding more fruit and vegetables to her diet, and boosting her calcium levels."

EMMA, 25

Height: 166cm
Weight: 58kg
BMI: 21 Size: 10
Pedometer count:
11,077 (weekdays)

12,950 (weekends)

TYPICAL DIET:

Breakfast: Special K with 99 per cent fat-free yoghurt and fruit, or two slices of raisin toast on weekdays. Scrambled eggs with sourdough toast, or toasted Turkish bread with Vegemite on weekends.
Lunch: Beef salad, tuna salad, or a falafel and hummus wrap on weekdays. Pumpkin soup with fresh bread on weekends.
Dinner: Roasted vegetable and goat's cheese salad, or moussaka with Greek salad on weekdays. Thai takeaway on weekends.
Snacks: Low-fat chocolate mousse, fruit salad, a piece of fruit.
Drinks (daily): Two litres of water, fresh orange juice, Nudie drink.
Alcohol (weekly): Approximately four bottles of wine, a few beers.
Smoker: Yes, socially - about 10 per week.
My body image: "I like my arms because so far I've managed to avoid the dreaded 'bingo wings' look! I also rely on them more since I started playing polo, as I need good upper-body strength. I'm most concerned about my legs. I think I've got wobbly thighs, and I really want to tone my legs and bum."
Exercise routine: "I make an effort to exercise for a solid hour three to four times a week, but I'll do some form of activity every day. Some days I'll do a cycle class at the gym, other days I'll run or walk, and on weekends I might go for a long bushwalk. I also play touch football once a week. I really enjoy working out, especially in the morning because it gets you pumped for the whole day."

Eating habits: "I've been on a few diets and counted kilojoules, but I've never really stuck to it. Once I've done it for a couple of weeks, I start craving the food I love and ditch it. I try to have a good breakfast every day and I rarely snack. My downfall is weekends, when I'm out drinking. I'm more likely to have takeaways or something unhealthy."

OUR EXPERT SAYS:

"By varying the intensity of her exercise and making it a social activity, Emma is setting herself up with a healthy exercise pattern she'll probably have for life. Her breakfast is relatively low in fat and it has lots of fibre. It's also full of complex carbohydrates and is low GI, which guards against hunger and insulin spikes. For her future health, she should quit smoking as she's putting herself at risk of heart disease and lung damage later in life."

VANESSA, 31

Height: 177cm
Weight: 72kg
BMI: 23 Size: 12-14
Pedometer count:
16,332 (weekdays)

18,067 (weekends)

TYPICAL DIET:

Breakfast: Yoghurt and fruit, or two slices of rye bread with avocado on weekdays. Salmon quiche or nothing on weekends.
Lunch: Fruit salad and yoghurt, or one piece of rye toast with avocado on weekdays. Nothing or a sandwich on weekends.
Dinner: Curry and vegetables followed by strawberries and mango yoghurt, or mushroom risotto and caesar salad (no dressing) on weekdays. Two Vietnamese rice paper rolls or a salad on weekends.
Snacks: Fruit.
Drinks (daily): Two or three skim flat whites, two green teas, several glasses of water.
Alcohol (weekly): Five glasses of red wine, three champagnes, two vodkas.
Smoker: No.
My body image: "I've always liked my height. I'm least happy about my arms because I think they're out of proportion with the rest of my body. There's a predisposition in my family to have an under-active thyroid, which can cause weight gain, so I'm conscious of eating well."
Exercise routine: "I do between 90 minutes to two hours of exercise each day - a mix of yoga, running (on soft sand) and walking. I feel good when I exercise and it motivates me to eat well. When you work long hours it's hard to incorporate exercise into your day, but I motivate myself to get up early before work, or I go to a yoga class in my lunch hour."

Eating habits: "I try to stay as healthy as possible during the week because weekends can be unpredictable. In the last two years, I've become more concerned about the nutritional value of what I'm putting in my body and I've become quite strict. If I want a snack, I'll have a piece of fruit instead of junk food."

OUR EXPERT SAYS:

"I'm impressed that Vanessa snacks on fruit. She is obviously committed to staying healthy, but overall her diet is unbalanced. While a lack of nutrients on the weekend might help maintain her weight by slowing down her metabolic rate, it's not a healthy pattern to be in. Vanessa also has to consider the possible damage to her spine and other weight-bearing joints, such as her knees and hips, from the amount and type of exercise she's doing. Maybe she should introduce something low-impact like swimming."

YOUR SAY

What comes first: size or health? We want to know how you view your 'healthy' body, so tell us by leaving a comment below.