Understanding the Need for Weight Control

The most important aspect of weight control is the amount of fat we eat as we get older. Fat is implicated in heart disease, stroke, breast, prostate and colon cancer, diabetes, and it's right at the heart, so to speak, of putting on the pounds.

Joe Schwarcz, Ph.D., and the editors of 'Foods That Harm, Foods That Heal' note that there are 'three facts beyond dispute' in any discussion of dietary fats: 'one, in small amounts, fats are essential to maintain health; two, the typical North American diet is much too high in fats of all kinds; and three, the fat debate is a gold mine for commercial exploitation of the popular pursuit of low-fat and fat-free alternatives to traditional foods.'

Why do we need lipids, as the family of fats (solid at room temperature), oils (liquid at room temperature) and related substances are known? To begin with, fats add flavour and texture to many foods, and satisfy our hunger long after we've completely digested the proteins and carbohydrates in our last meal. Fat's also the transport vehicle for fat-soluble vtamins A, D, E and K in the body, and provides the body with fatty acids essential to all kinds of body processes, from growth and normal metabolism to the manufacture of sex hormones and cell membranes.

Stored body fat serves a number of other functions. The layer of subcutaneous fat just beneath your skin is an insulator against the cold and a factory for vitamin D production under the sun; other fat deposits cushion and support the vital organs, protecting them from injury. Fat is also nature's way of preparing you for the next famine, providing a day-and-a-half to two days' worth of energy for every pound of stored fat.

Since few of us, though, will ever have to make emergency withdrawals from the fat bank, any extra deposits we make now become joint-stressing and artery-choking liabilities later. Fat's different from anything else you ingest. It's not just because fat is, well, fat, but because of the way our bodies take it in. On a gram-for-gram basis, there are twice the number of calories in fat as in carbohydrates and protein. In itself, that doesn't explain fat's precocious ability to turn us into butterballs. The key is that, if you eat a fruit, a vegetable or a slice of bread, your metabolism turns on and breaks it down. Fat's different: 90 per cent of all the fat we eat gets stored on our bodies. If it goes in, in other words, it goes on, and it takes a lot of effort to get it off again.

Thus, the most important aspect of weight control is the amount of fat you eat; Canada's Food Guide recommends trying to keep it to 30 per cent or less of your daily food intake. It's worth noting that the average North American's daily fat intake hovers between 35 and 40 per cent at the moment, which is six to eight times more than anyone actually needs. But even more important than the amount of fat is the kind of fat you ingest — which brings us to cholesterol.

Cholesterol, of course, is the big name in the world of fats, and it's usually dressed in villainous black. In fact, the body does require some cholesterol—to help in the manufacture of sex hormones, cell membranes and the sheathing on nerve fibres, among other things — but we don't need it from our diets. The waxy, fatlike compound is produced in ample amounts, thank you, by the liver; the cholesterol we ingest in animal products is superfluous and — depending on your genetic makeup, gender, how much exercise you get and what else you're eating — potentially fatal.

The problem with dietary cholesterol is that it tends to build up on artery walls, which can lead to atherosclerosis (narrowing of the arteries) and heart disease. Helping cholesterol perform this insidious task are lipoproteins, or lipid-carrying proteins: Low-density lipoproteins (LDLs), known far and wide as 'bad' cholesterol, deposit cholesterol on artery walls, while high-density lipoproteins (HDLs) — the 'good' cholesterol — scrape cholesterol deposits from blood vessel walls and haul it off to the liver to be processed and eliminated.

As Schwarcz et al point out in 'Foods That Harm...', that's where the type of fats consumed comes into play: 'Highly saturated fats raise blood cholesterol levels because they interfere with the removal of cholesterol from the blood. Monosaturated and polyunsaturated fats, by contrast, either lower blood cholesterol or have no effect on it. When polyunsaturated fats are hydrogenated [that is, hydrogen is added] to make them firm, they become like saturated fats in their effects on blood cholesterol.'

The main sources of saturated fats are animal products, but many of those fats are 'hidden' in meat, milk and cheese, says Monica Vegelji, a registered dietitian at The Toronto Hospital. 'When you're eating a slice of cheese, it's difficult to see the fat — it's not a fat like margarine or butter that you'd spread on a piece of bread that's easily visible and identifiable, or, for example, the hidden fat in a muffin: It looks like a grain product, but fat has gone into its preparation.'

Whenever possible, check nutrition labels on food products to see whether the fat content's been broken down as monounsaturated, polyunsaturated and saturated. 'Chemically there's a difference between poly- and monounsaturated fats, but in terms of the physiological impact they're both considered to be the better quality of fats,' Vegelji says, 'and it's good to get some source of unsaturated fat in a day. A good source of polyunsaturated fat would be corn oil, sunflower oil or safflower oil. A good source of monounsaturated fats would be olive oil, canola oil or peanut oil.'

Too much of any kind of fat can lead to a high cholesterol level, so the key is to achieve a balance, Vegelji says. Ideally, for most people, the total fat from one day's food consumption ought to add up to between one and two tablespoons — about two teaspoons per meal over three meals. Keep in mind that a pat of butter or margarine, or a tablespoon of ordinary salad dressing, contains a teaspoon of fat, while just one commercially prepared muffin will have about three teaspoons—or two meals' worth — of fat. A 50-gram bag of potato chips will be about one tablespoon of oil. So, there's room for those kinds of things, Vegelji says, 'but in small quantities.'

To turn yourself into an effective fat-fighter, check out Canada's Food Guide, then ask your doctor for a referral to a dietitian to make sure you're optimizing your healthy food choices.

You may also want to visit the Dietitians of Canada Web site at http://www.dietitians.ca. This site is an excellent source for your nutrition information. Be sure to visit their Eat Well, Live Well section. It's special features include Your Nutrition Profile, Meal Planner, Healthy Body Quiz, Virtual Kitchen and Frequently Asked Questions/Factsheets.

This page was last reviewed/updated on : 02/23/2008