A steady surplus of calories can dramatically increase the risk of many types of cancer
As I listened to the presentations at last week’s American Institute for Cancer Research Annual Research Conference in Washington, it became clear to me that obesity has become our No. 1 public-health enemy.
Maintaining a healthy weight through adulthood is key to preventing Type 2 diabetes, high blood pressure, heart disease and – according to a growing body of evidence – cancer.
That’s not to say excess sodium, refined sugar and trans fats don’t wreak havoc. Or that a diet lacking fruits, vegetables, whole grains and legumes doesn’t increase one’s risk for certain diseases.
The quality of your diet is an important predictor of health. But a steady surplus of calories can also dramatically increase the risk of many types of cancer by packing on the pounds.
Indeed, the majority of sessions during the two-day conference focused on the role of obesity in cancer risk.
Carrying excess body fat is strongly linked to cancers of the breast, endometrium (lining of the uterus), kidney, colon, pancreas and gallbladder. What’s more, the list of cancers affected by obesity is expected to increase as research continues. Some studies have also linked liver cancer, multiple myeloma and certain leukemias to obesity.
If your body mass index (BMI) is 30 or greater, you’re considered obese. BMI is calculated as your weight in kilograms divided by the square of your height in meters. For most people, having a BMI of 30 means being about 30 pounds overweight.
Obesity is thought to boost cancer risk in a number of ways. Excess body fat increases levels of the female hormone estrogen, which can increase the risk of breast and endometrial cancers after menopause. Obesity also leads to gastrointestinal reflux, which is linked with a higher risk of esophageal cancer.
Being overweight also causes increases in insulin and other proteins that stimulate the growth of cancer cells.
The message was straightforward and powerful: to lower your risk for cancer you need to manage your weight, exercise and eat healthfully.
The formula for losing excess weight – or preventing weight gain – is pretty simple: Burn more calories than you consume. But based on the number of overweight and obese Canadians, it would appear that 51 per cent of us have trouble following this prescription.
Overeating calories is easy to do in a world where large portions of high-calorie foods are widely available, low in cost and heavily promoted. Coupled with an environment that discourages physical activity – cars, television, computers, remote controls – it’s no surprise that our nation’s waistline has steadily expanded over the past three decades.
To manage your weight, you need to consider calories – not high protein, low fat, or the glycemic index, for that matter. It’s the number of calories you eat that will determine whether you lose weight, gain weight, or hold steady.
The first step in weight control is knowing how many calories you currently consume – a number that most people aren’t clued in to. In fact, studies show that consumers tend to underestimate their calorie intake. Unless you’re working with a dietitian, you’ll have to figure this out on your own.
To do so, keep a food journal for three weekdays and one weekend day (people tend to be more relaxed about their food intake on the weekend). Writing it down will make you aware of those mindless nibbles that sneak in during the course of the day – and it will highlight the healthy foods that you might not be eating enough of.
Track the calories for everything you eat and drink. Pick up a calorie counter at the bookstore or determine your calorie intake online. Check out www.foodcount.com, a website sponsored by the U.S. Department of Agriculture. Then tally the total number of calories and divide by the number of days you tracked.
Next, determine how many calories you need to maintain or lose weight. Calorie needs depend on age, weight, gender and activity level.
Sedentary women aged 31 to 50 need roughly 1,800 calories to maintain their weight; men need about 2,200. If you’re moderately active – 30 minutes each day – women can consume 2,000 calories and men can eat 2,400. If you’re very active – 60 minutes or more per day – women need about 2,200 calories while men require 3,000. (These calorie requirements are based on people of average height and weight required to maintain a BMI of 21.5 for women and 22.5 for men.)
Our bodies run on fewer calories as we get older, since our resting metabolism – the number of calories a day required to simply maintain breathing, heart rate and body temperature – declines by 1 to 2 per cent each decade. After the age of 50, daily calorie requirements decrease by about 200.
Theoretically, you’d have to consume 500 fewer calories each day to lose one pound a week, since one pound of body fat stores about 3,500 calories. You can do this by cutting 500 calories from your diet, or by a combination of eating less and burning calories through daily exercise.
Depending on the amount you’ve been overeating, you may be able to cut 1,000 calories from your daily diet, which would lead to a weekly two-pound weight loss.
Once you know your daily calorie budget, you can create a menu plan to use as a guide. Spend your calories wisely by choosing mainly nutrient-rich foods such as lean protein, whole grains, fruits and vegetables.
Learn what 100 calories worth of food looks like. You’ll find it’s easy to drop 100 calories from meals and snacks with simple changes.
Read the calorie information on food labels. Beware of how many calories are in one serving and how many servings you typically eat.
Getting a rough idea of how many calories you typically consume and how many you actually need is an eye-opening experience – and one that can make a big difference to your health.
HOW MUCH FOOD IS 100 CALORIES*?
Protein foods
Lean meat, chicken
2 ounces (60 g)
Fish, salmon
2 ounces (60 g)
Fish, tuna
3 ounces (90 g)
Eggs
1 large
Cheese, part skim
1 ounce (30 g)
Cottage cheese, 1%
½ cup (125 ml)
Chickpeas, cooked
1/3 cup (75 ml)
Milk and milk alternatives
Milk, skim or 1%
1 cup (250 ml)
Yogurt, 1% MF
1 cup (250 ml)
Soymilk, plain, enriched
1 cup (250 ml)
Starchy foods
Cereal, e.g. Bran Flakes, Cheerios
1 cup (250 ml)
Cereal, 100% Bran
½ cup (125 ml)
Oatmeal, cooked
¾ cup (175 ml)
Pasta, cooked
½ cup (125 ml)
Popcorn, air popped
3 cups (750 ml)
Rice, cooked
½ cup (125 ml)
Whole grain bread
1 slice
Fruits
Apple, pear
1 medium
Apricots
3 whole
Banana
1 medium
Blueberries, strawberries
1 cup (250 ml)
Dates
5
Fruit juice, unsweetened
¾ to 1 cup (175 – 250 ml)
Prunes
dried 5
Raisins
¼ cup (50 ml)
Orange
1 large
Fats and oils
Almonds, unsalted
14 whole
Avocado
Peanut butter
1 tbsp. (15 ml)
Sunflower seeds
2 tablespoons (25 ml)
Vegetable oil
2 teaspoons (10 ml)
*Calorie values range from 90 to 115
Leslie Beck, a Toronto-based dietitian at the Medcan Clinic, is on CTV’s Canada AM every Wednesday. Her website is lesliebeck.com .
CTVglobemedia Publishing, Inc
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