The advice for weight control used to be simple: eat less and exercise more. But emerging research suggests that not all calories are created equal. That bowl of frosted cereal for breakfast has a completely different impact on your body than an equivalent serving of oatmeal with fresh berries. Here are some of the foods that seem to contribute most to widespread obesity, and those with the most promise to help us slim down.

THE OFFENDERS

The sugar trap

Naturally occurring sugars in fruit, vegetables and dairy products give us necessary energy. But the added sweet stuff in our diets not only racks up empty calories, it numbs our cells to insulin, making the heart work harder to pump it out and bring blood sugar down to a normal range. Sugar that is not consumed by the body is also more likely than other calories to be stored as fat. Worse, perhaps, is that sugar releases feel-good opioids and dopamine in the brain and that high is habit-forming. According to researchers at the University of Tennessee, the increase in adults living with obesity is linked to the long-lasting effects of the high-sugar diets among children in the 1970s and 1980s.

Convenient caloriesThat a frozen pizza contributes more to obesity than a salad is no big surprise. But according to a recent report in Cell Metabolism, the first randomized, controlled trial of its kind, the problem is not simply bottom-line caloric intake or levels of macronutrients such as fats.

Over a period of one month, 20 healthy adult volunteers were admitted to the National Health Institutes Clinical Center in Maryland. For two weeks, they were given ultra-processed meals, bagels with cream cheese and turkey bacon, for example, or frozen dinners. For the other two weeks, they were fed unprocessed foods such as oatmeal with fruit and diners such as roast chicken with rice and peas. Both diets contained the same number of calories and the same amount of fat, fibre and carbohydrates. The key difference between the two menus: ingredients predominantly found in industrial food manufacturing, such as hydrogenated oils, high-fructose corn syrup, flavoring agents, and emulsifiers.

The results were stark: Those on the ultra-processed diets ate faster, and about 500 calories more per day, than those on unprocessed diets. In fact, those on the unprocessed diets lost weight. Why processed foods led to these differences remains to be studied, but the scientists conclusion heavily processed foods cause overeating and weight gain in and of themselves.

Those on the ultra-processed diets ate faster, and about 500 calories more per day, than those on unprocessed diets

Potato chip pile-onClearly, chips arent a health food. Theyre loaded with salt and fried in oil, and people mindlessly crunch through large portions. How bad are they? Harvard University scientists say they are thebiggest culprit behind the pound-a-year weight creep.

By analyzing data collected over 20 years from more than 120,000 men and women in the U.S. who were not obese and were free of chronic diseases, researchers identified a number of specific foods linked to weight gain. Potato chips were the biggest offender: a daily one-ounce serving about 15 chips and 160 calories led to a 1.69-pound increase over four years.

As for healthier veggie sticks and straws? Theyre like a wolf in sheeps clothing, says Anna Taylor, a registered dietitian at the Cleveland Clinic. (They) lack fibre and protein, and are practically devoid of nutrients.

Grab-and-go smoothiesUnless you make them yourself, smoothies often come with hidden sugar and calories mainly from juice. But the fact that these drinks can pack as much sugar as a few bags of candy is only part of the reason they contribute to obesity. Nutrition and behaviour scientists at theUniversity of Bristol have found thatfruit smoothies and other energy-containing drinks are also less satiating than whole foods. We can gulp down anywhere from 300 to 700 calories of a spinach-and-berry-filled drink that wont keep us feeling as full as a whole-food option such as fruit slices with nut butter.

Refined grainsMany people think of carbs as the enemy when it comes to weight loss. But its important to focus on the right target: white rice, white bread, white pasta and all-purpose flour all of which lack the fibre and key nutrients of their whole-grain counterparts and carry a high glycemic index. The glycemic index is a scale that ranks carb-loaded foods by how much they raise blood sugar. Spanish nutrition researchers reviewed abody of research on diet and obesityand found that people who regularly consume refined grains, as well as other foods with a high glycemic index, have more difficulty managing their weight.

THE HEROES

Nuts to that

Not all fats are a four-letter word. Anew study published in the online journalBMJ Nutrition, Prevention & Healthfound that eating a handful of nuts on a regular basis may help prevent excessive weight gain and lower the risk of obesity. Thats because most of the fat in nuts are good for us: monounsaturated fat, as well as omega-6 and omega-3 polyunsaturated fat, are essential to protect our organs, help us absorb nutrients and produce important hormones.

Researchers also say that the fat, protein and fibre combination in nuts takes longer to digest than foods with just carbohydrates and protein, keeping us feeling full longer. They found that a consistent intake of at least a half-ounce of nuts a day was associated with a 23 per cent lower risk of putting on 10 or more pounds over a four-year period. An added bonus, when nuts became a regular part of participants diets, their unhealthy food consumption decreased.

Beans and lentils

The biggest obstacle to lasting weight loss is also the most obvious: hunger. Eating protein at every meal can help, says Alexandra Johnstone, a specialist in obesity and metabolic health at the Rowett Institute of Nutrition and Health at the University of Aberdeen. Plant-based proteins, such as beans and lentils, can also have a positive impact on the trillions of bacteria and microorganisms that live in our digestive tract, according to astudy presented this October at the United European Gastroenterology Week in Barcelona. A healthy gut is foundational, responsible for better food absorption and overall system regulation.

Fermenting is your friend

Naturally fermented foods are also getting a lot of attention from health experts because of their role in strengthening our gut microbiome. Researchers have linked the loss of healthy bacteria and microorganisms to all sorts of health conditions, including obesity. Foods like kombucha tea, kefir, kimchi and sauerkraut are preserved using a traditional process that boosts food shelf life and nutritional value, and provide a dose of healthy probiotics, the microorganisms essential to healthy digestion.

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What to eat (and avoid) if you're trying lose weight - National Post