The best dietary advice for a nation battling the bulge comes from the experts.
Question: I am in my fifties, having struggled with weight all my life, and am now down to a healthy weight. I feel great, look good, eat a diet based mainly on vegetables – with the barest amount of anything processed – and 
walk a minimum of three hours a day. I love my life but I am constantly being told that I should be eating this, that and the other thing. Whatever happened to what feels right for you?
Answer:
Congratulations on getting yourself to a healthy weight and a place where you feel good about your health and life. This is a significant achievement when we live in an obesogenic environment. We may think maintaining a healthy weight comes down to personal choice and a good dose of willpower, but a significant body of research suggests otherwise.
Indeed, a recent Lancet report went so far as to say that obesity is a perfectly normal response to the obesogenic environment, in which a global food system is producing more and more cheap, processed, energy-dense, cleverly-marketed foods that are highly accessible and convenient.
In New Zealand, weight problems have ballooned in the past 12 years, according to the recently released 2008-09 New Zealand Adult Nutrition Survey (NZANS). In 1997, 17% of New Zealand men were classified as obese, compared with the new survey’s 27.7%. For women the rate has gone from 20.6% to 27.8%. Although obesity rates are higher among Maori and Pasifika groups, New Zealand European and other ethnic groups’ rates have also shown a marked increase.
Strangely, the survey found that although New Zealanders were gaining weight, their daily energy intake had decreased. It’s been suggested that decreased physical activity levels, rather than increased food intake, must therefore be causing our waistlines to grow.
Although Bronwen King, public health nutritionist at Partnership Health Canterbury, agrees that lack of physical activity may be contributing to our weight problems, she says this is just a drop in the ocean. “Weight gain is far more complex than simply energy in versus energy out,” she says.
“The type of kilojoules consumed can influence weight gain. Kilojoules that come from sugar and other refined carbohydrates enter the blood stream quickly [and] cause fast, sharp rises in blood glucose, which in turn generate a large insulin response.
“Since insulin promotes fat storage, people consuming a highly refined diet are likely to be more prone to insulin resistance, to type 2 diabetes and to storing fat and gaining weight.”
Other factors that influence weight gain include “hormones, stress levels, lack of sleep, the speed at which we eat, television watching and even our work practices”, says King. Many people may also under-report their true food intake.
Nutritional science and weight maintenance are complex topics. Registered dietitians and degree-qualified nutritionists understand the science behind what may appear to be simplistic healthy-eating advice.
The media carry abundant nutrition advice but much of it, unfortunately, is contradictory. It’s common to report on single studies, particularly when they contradict accepted healthy eating advice. This doesn’t mean the research is incorrect but it must be weighed up against the body of existing evidence. It’s worth bearing this in mind whenever someone offers advice at odds with generally accepted guidelines.
Most people don’t appreciate unsolicited nutrition advice, unless it comes from a close relative or friend. If the person offering you advice is someone close to you and is genuinely concerned about how you’ve attained and maintained your weight loss, then it’s worth bearing their thoughts in mind.
Although eating lots of vegetables is great, it’s not clear from your letter whether you have a balanced diet that provides enough protein, calcium, iron and other important macro- and micronutrients. A visit to a dietitian or nutritionist would clarify this and ensure you have a healthy, balanced diet that promotes both healthy weight maintenance and good long-term health.