Are you gaining weight a little more easily than you used to? And finding it harder to shed? 

The first thing to check is your kilojoule intake and exercise output: overeating and
under-exercising are still the basic reasons we gain weight. And just being on your feet all day is not exercise, although any incidental activity has benefits – the exercise we need involves a sustained higher respiratory rate. If the intake-output equation balances, then a sluggish metabolism – the process whereby the body converts nutrients into energy – may be to blame.

The basal metabolic rate (BMR) is what keeps us alive even when we’re asleep or crashed out on the couch. Sadly, this slows with age, so post-40 a woman can gain up to half a kilo a year if she eats the same way as pre-40. As we get older, we need to eat less and exercise more to avoid the muscle mass loss, as muscle activation is a fat-burning mechanism. Having few mitochondria, a fat cell produces little energy; a lean muscle cell, however, has upwards of 1000 mitochondria, so it can produce much more energy. By reducing the number of fat cells and increasing muscle cells, you up-regulate the body’s ability to transform its fuel into energy. Whether or not you lose weight when you start to exercise – some people actually gain weight initially as they add muscle – your BMR is increasing.

Metabolism influencers

* Genetic factors: May cause metabolism to be less efficient; look at your family to identify the thrifty gene that enables you to accumulate weight quicker than others.
* Height: Tall people have a higher BMR as they have a greater skin surface for heat loss, which raises BMR. Short people have to work a little bit harder.
* Stress: This is one of the most important factors in the metabolic rate, making de-stress techniques critical.
* Hypothyroidism: Your GP can check T3 and T4 hormone levels to identify this. Few people have true hypothyroidism, but we do know that one in three people tested in Sydney in 2005 had iodine deficiency, and so may have had a mild hypothyroid.
* Medications: Can affect thyroid function.
* Fever: It slows metabolism.
* Sleep: Sleep duration actually affects the regulating hormones ghrelin and leptin. Sleep deprivation is also associated with increased appetite for high-kilojoule foods.
* Skipping breakfast: Research shows this slows metabolism.
* Starving yourself: This does not help you lose weight, and it doesn’t improve your metabolism; in fact it makes it worse.
* Consuming fewer than 1200 calories (5000 kilojoules) a day: Low-kilojoule diets slow the metabolic rate, and cause muscle mass to break down for energy. So even when dieting, it’s important to consume at least 1300 calories (5450 kilojoules), eating every three to four hours to prevent that muscle-mass breakdown.
* Agricultural chemicals: Canadian researchers report that people who consume foods polluted with organochlorines store these chemicals in their fat cells. When they attempt to lose weight, they experience larger than usual dips in their metabolism. We don’t know how, but we do know the toxins from organochlorines interfere with the energy-burning process. Eat organic foods whenever possible, or least soak conventionally-farmed produce in a mixture of one cup of plain white vinegar and four cups of filtered water for a couple of minutes to remove some of the chlorines. Or, buy from local farmers markets and ask vendors about their spraying techniques.
* Alcohol: Avoid or limit consumption, because the body uses alcohol rather than food as the preferred fuel to process alcohol. So if you have two glasses of wine, you actually reduce your body’s fat-burning ability by up to 73 percent.

A helping hand

Caffeine and catechins: Coffee is a central-nervous-system stimulant, raising metabolism by about five to eight percent: one cup can burn about 98 kilojoules. Brewed black tea and green tea can raise the metabolism by about 12 percent, according to Japanese studies, with the catechins providing the boost.
Protein: Adding some good protein to every meal or snack – approximately 80 to 100 grams of lean meat, nuts or yoghurt – increases satiety, so you eat less. Plus, protein breakdown requires considerable energy due to its quaternary structure: around 35 percent of the kilojoule intake. Carbohydrates, including whole grains, require just 15 to 18 percent of the kilojoules.
Vitamin D: This appears to be essential for preserving the metabolising power of lean muscle mass. The minimal erythemal dose is 15 minutes morning and evening, but as we get older supplements are necessary as our ability to manufacture vitamin D from sunlight declines markedly. Further, any medication that upsets the liver or kidneys hinders the conversion of vitamin D to its active form.
Iron: Maximise intake, as higher levels are necessary to oxygenate muscle so it can burn fat. But don’t self-prescribe supplements: have your GP check your iron levels and if they’re too low, consult a natural health practitioner who can help you to increase iron-rich foods and maximise its absorption by combining foods.
Thermogenic spices: Ginger, chilli, wasabi, and cinnamon increase thermogenesis: they actually turn up the heat in the body, which can boost metabolism by about five percent and increase fat-burning by about 16 percent.

Teresa Mitchell-Paterson, BHSc (Comp Med) MHSc (Hum Nut) Adv Dip Nat, is a member of the Australian Traditional-Medicine Society.