By Matt O'Neill, MSc(Nut&Diet), APD
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Some foods are better than others for helping you stay in shape? But are there foods and eating habits that are must-haves for a healthy metabolism? In this article I'll show you how to eat for a healthy metabolism in four ways.
Many people think of metabolism as the rate at which our bodies burn calories. If you've got a slow metabolism you tend to gain weight easily whereas a fast metabolism keeps you lean.
But metabolism encompasses much more. It represents all the chemical reactions in your body. To make sense of how they work together to keep in or out of shape think of eating for your metabolism as having four components; energy burning, appetite regulation, hormonal balance and nutritional optimisation. Looking after each component is vital for achieving your best shape and physical performance.
1. Eat to maximise energy burning
This first component relates to calorie burning, so the key questions here are whether certain foods and eating patterns can burn more calories.
Of the macronutrients, protein has the highest Thermic Effect of Feeding (TEF) when compared to fat, carbohydrate and alcohol. TEF describes the energy cost of digesting and absorbing food. It takes more energy to break down protein. Aim for a minimum of 1 gram of protein per kilogram of body weight and a maximum of 2 grams per kilogram.
What about specific foods? Research on chilli reveals the active ingredient capsciasin can stimulate metabolic rate but is only likely to do so at levels that are unpalatable to all but the hardiest chilli lovers.
Green tea contains antioxidants called catechins which are thought to kick metabolic rate up by about 70 calories a day when consumed is sufficient quantities. Around four to five strong cups of green tea each day is a minimum.
When it comes to eating habits and meal timing, it's the total amount of food that you consume in 24 hours that matters. Around 15 percent of our resting energy expenditure is accounted for by TEF. If you eat more, this figure increases. If you eat less, as is the case with dieting then the TEF percentage will drop a little. Crash dieting will cause a further drop in your total metabolic rate as your body attempts to conserve energy.
As long as you keep your total daily calorie and macronutrient balance the same, diets of three or six meals will have the same affect on daily TEF.
2. Eat to re-wire your appetite
Appetite is the next component of your metabolism. In recent years, scientists have started to untangle the complex ball of biological reactions that make up appetite chemistry.
The theory part of appetite regulation says you should eat when you are hungry and not eat when you aren't. In practise it's a challenge because many of us have had our appetites hotwired to overeat from a young age.
Eating for your metabolism means recruiting your natural appetite chemicals to work for you automatically. For example, the gut hormone cholecystikinin (CCK) is released 10 to 20 minutes after you start eating and sends a message to your brain that you are being nourished. Slowing you eating rate at meals gives CCK a chance to do its job.
Ghrelin is another hunger-related hormone. It triggers a strong signal to eat 4 to 5 hours after your last meal. Skipping meals plays havoc with ghrelin and can drive you to overeat at your next feeding session.
While researchers continue to study dozens of gut and brain-based appetite chemicals, almost all the journal articles highlight the importance of re-wiring your appetite chemistry. This is done by eating regularly (at least three meals a day) and carefully listening to your appetite chemicals to know when you need to eat and stop eating.
Foods that contain protein, especially meat, fish, chicken and other animal protein sources tend to suppress appetite the most. Low-glycaemix index (GI) carbohydrate foods like oats, pasta, legumes and some wholegrain breads are better at making you feel fuller for longer than more processed high-GI foods like white bread, rice and sugary treats.
3. Eat to balance your hormones
The major metabolic hormone is insulin, which regulates the storage of blood glucose as muscle and liver glycogen. Eating the right amount of food, particularly low-GI carbohydrates spread over meals and snacks keeps insulin levelled and functioning properly.
Overeating and subsequent body fat gain interferes with insulin function causing insulin resistance and additional weight gain. When weight gain results in obesity, growth hormone levels often fall and the spiral of metabolic dysfunction can spin out of control.
Eating for healthy hormone metabolism also means consuming enough of the mineral iodine. Iodine is necessary for your thyroid to secrete the thyroid hormones that maintain your metabolic rate.
Including seafood two to three times a week, plus meat, eggs and a multivitamin in your diet plan will help you get the iodine you need. Seaweed products can also give your iodine levels a boost as can brazil and hazelnuts.
Other hormones may be more susceptible to non-dietary influences. Cortisol, which is known as the stress hormone can trigger food cravings by stimulating the hunger chemical neuropeptide-Y in the brain. Managing stress therefore has a direct benefit on metabolic fitness.
4. Eat to optimise your nutrition
The fourth way to eat for your metabolism is to aim for nutritional optimisation. This is the nutritional equivalent of financial superannuation. Your investment now ensures a metabolic payoff in the future.
Dairy foods are a good example. A growing body of research suggests an adequate intake, say at least two serves a day, is required to promote healthy body fat levels. It may be the calcium, something else in dairy or a combination that seems to enhance fat burning.
Omega-3 fish oils have a similar story. It's thought that a generous intake from fish or fish oil capsules helps positively regulate fat burning. One study found a 1.6 kg greater reduction in body fat in a group that took 6 fish oil capsules ( 6 x 1000mg capsules, each containing 300mg fish oils) each day over 16 weeks compared to the group who took the non-fish oil placebo. Experts are still sketchy on the mechanism, but it has something to do with the incorporation of the long-chain fatty acids into cellular membranes.
The metabolic and weight management cases for eating a nutrient-rich diet are growing and has lead to one academic coining the terms `malnutritive obesity' or `malnubesity'. This refers to the development of obesity triggered by nutrient deficiencies or imbalances. Even a higher protein intake will be sub-optimal if the level of protein pushes other nutrient-rich foods out of your diet.
Look after your metabolism four ways
This article has built a case to eat for your metabolism in four ways. Firstly, avoid crash dieting and use protein to boost metabolic rate. Then keep your appetite chemicals working with rather than against you. Eating to balance insulin, ensuring enough iodine and managing stress are next. Finally, hedge your metabolic bets by eating from all the food groups and demanding nutrient-rich food at every meal.
The diet that keeps you in shape should focus on more than calorie counting and metabolic rate. Eating for your metabolism four ways is the key to automatic lifetime results.
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