An important nutrition principle is the one of replacement: for every food (or nutrient) you remove from the diet, another usually takes its place.

One common limitation I see with many popular diets is that they fail to appropriately advise on replacement. Low sugar, low fat and low carb can each be effective for better health and body weight. But they can each be pointless exercises, too.

To demonstrate, consider these well established research findings:

• Replacing sugar (and other carbohydrates) with protein reduces weight gain. Yet replacing sugar with other carbohydrates (starchy foods like white bread, rice and crackers), does not.
• Replacing fat with protein and fibre reduces body weight. Yet replacing fat with carbohydrate, does not.
• Replacing carbohydrate with polyunsaturated fat (found in sunflower, safflower and soybean oil, and a variety of nuts, seeds and oily fish) reduces heart disease risk. Yet replacing carbohydrate with saturated fat (found in some meats, dairy and butter), does not.

Talking about what to eat less of, matters. But talking about what to eat instead, matters even more.