Burning Questions About Metabolism

On the topic of metabolism and weight loss, conflicting information abounds. Here are the highlights of some recent studies:
Does too much restriction of food intake really slow one’s metabolism? If so, how much and at what level of calorie reduction does this kick in?
On the first question: Yes, which is among the many reasons why starvation diets don’t work. Any time a person drops below 1,200 calories a day, the body shows signs of slower basal metabolism,” Research shows anything less than 1,000 calories per day would prompt slower metabolism. As soon as you cut calories significantly, you’re not the same person metabolically.
Does the number of meals you eat impact your metabolic rate?
No, but it can impact hunger and energy levels. Eating 7 meals a day was the same as eating 2 meals a day, so long as total calorie intake was the same. There is also evidence that small, frequent meals stabilize glucose levels — which in turn can control hunger. Keeping insulin and glucose at a steady state is the best way to maintain a ‘healthy’ metabolism.
Does working out harder extend your metabolic burn beyond the time of the workout itself? For example, does it extend the calorie burn deeper into the day if you work out hard for 20 minutes rather than for 20 minutes moderately?
Yes. The exercise afterburn effect directly affects metabolism and is stronger after a hard workout. Intensity is more important than duration, according to a 2003 Norwegian study. For a few hours after a hard workout, your hourly calorie burn rate would equal 15% to 20% of the total calories used during the workout. A moderate workout would yield only a 10% post workout calorie burn. For instance, someone who did step aerobics for 30 minutes and expended 400 calories would have an afterburn effect of 60 to 80 calories per hour. And a person who walked for an hour and burned 500 calories would have an afterburn effect of about 50 calories.
Are there supplements and herbs that can increase metabolism?
Yes, but there’s not a lot of solid science behind them. Green tea and caffeine are the most studied supplements in terms of metabolic boost. A 2007 study in the journal Obesity that found drinking a beverage containing green tea catechin, caffeine and calcium 3 times a day increased 24-hour energy expenditure by 4.6% in healthy, young, lean men and women. The real value of these supplements is not that they ‘increase’ metabolism but rather that they help to prevent metabolism from dropping as you lose weight.
Are there really foods that increase metabolic burn?
No foods have the magical quality to burn the calories away. However, there is a thermic effect to food — the digestion process burns calories and boosts metabolism. Protein has the highest thermic effect, followed by carbohydrates. Fat has almost no thermic effect. A Dutch study that concluded that eating omega-3 fats can boost metabolism, while saturated fat consumption slows metabolism.

Again, remember the bottom line: Fresh produce, whole grains, lean protein and low-fat dairy are better than processed, sugary foods. And to lose weight, you must burn more calories than you consume. And that is a clear message we can give our patients.

Content adapted from Revolution Health Group