A Calorie Is Not A Calorie
All calories are created equal. Right? After all, it's simple physics. One hundred calories of, say, table sugar, is the same as 100 calories from broccoli. Right? That's certainly been the message we've all been told for decades. To lose weight, you simply have to burn more calories than you consume.
Makes perfect sense. Sure, 100 calories worth of broccoli takes up more space than 100 calories of ice cream ( a lot more!). But ultimately, it's all the same. If you burn these vastly different foods in a lab, for instance, they both release energy equal to 100 calories. In the lab, all calories are created equal.
Except, in the real world, they're clearly not.
For one thing, your body is not a laboratory crucible. It's a highly complex system. The foods you eat affect your body in numerous ways. Different foods affect your feelings of hunger/fullness (satiety) differently, for instance. Ditto blood sugar levels, metabolic rate, brain activity, and various hormones that influence fat storage and other processes. Foods can also influence inflammation, which plays a role in numerous common diseases. Some foods encourage inflammation. Others turn down the flames.
For another thing, calories from different foods are absorbed differently. When we eat high-fiber foods like nuts and non-starchy vegetables our bodies only extract about three-fourths of the calories in these foods. The rest pass through, unabsorbed. The same can't be said for calories from simple carbohydrates, such as table sugar, pasta, or white potatoes. In general, foods with a low glycemic index (GI) tend to affect the body differently than high-GI foods.
The glycemic index is a system that tells you something about how a given food will affect your blood sugar in the short term. High-GI foods, like sugar, potatoes, white rice, and white bread, tend to cause rapid, steep spikes in blood sugar levels. Low-GI foods, like beans, seeds, nuts and even most sweet fruits, tend to cause relatively small and steady increases in blood sugar.
The bottom line is this: The notion that you can lose or maintain weight by eating whatever you want—as long as you pay attention to calories—is simply wrong.
It's overly simplistic, and it doesn't account for the beneficial metabolic and appetite-suppressing effects of certain kinds of foods. Nor does it account for the harmful effects of other kinds of foods. In general, consuming about 2,000 calories a day of whole foods; including whole grains, vegetables, fats, protein, nuts, seeds, and fruits, should serve you well. And fats. We now know that fat is not the enemy. On the contrary, it may be one of the keys to managing weight, due to its effects on appetite. A diet featuring 2,000 calories from simple carbohydrates and processed foods will encourage weight gain. So it's time to rethink the whole calorie-counting approach to weight control. It misses the crucial point that it really does matter where those calories are coming from. Think more protein, fats, and whole foods, and fewer simple carbs and processed foods.