Fat-Loss Studies

Here are a few recent studies on the science of fat loss.

1) Artificial sweeteners increase appetite.
Purdue University researchers discovered that rats given snacks with artificial sweeteners had impaired ability to compensate for the calories in the snack. At mealtimes, they ate more and gained three times more weight than rats fed normally sweetened snacks. It is not clear if this study translate into human behavior as well or if the rats' response was species specific.
[Int J Obesity, 28: 993-935, 2004]

2) What is the best exercise intensity for fat loss?
Researchers at UC Berkeley have found that the body prefers to burn fat for energy while at rest and at low exercise intensities. At above 65 percent of maximum effort, the body quickly shifts to primarily carbohydrate use for fuel. The rate of fat cell breakdown for energy decreases rapidly with higher exercise intensities. So to lose fat, one should exercise at low to moderate intensity, right? Wrong!

While it is true that low-intensity exercise burns more fat during exercise, you actually burn more fat during a 24-hour period following high-intensity exercise than after low-intensity exercise. High-intensity exercise burns more calories during the exercise bout and increases metabolic rate following exercise, thus burning more fat while at rest during the post-exercise period.

To maximize fat loss, exercise at as high an intensity as you can.
[Nutrition, 20: 716-727, 2004]

3. Lack of sleep increases obesity risk.
In a study that has been widely reported in the mainstream media, researchers at the U.S. National Institute of Mental Health found that lack of sleep increases the risk of obesity. The study followed nearly 500 people over 13 years. The people who gained the most weight were those who lost the most sleep as they aged.

One possible mechanism for this outcome is the reduction in leptin levels that occurs with reduced sleep. Leptin is one of the body's chemicals that controls body fat stores. Lower leptin levels results in increased appetite and slower metabolism.
[Sleep, 27: 661-666, 2004]

4. A calorie is not a calorie.
Nutrition researchers from the University of Wisconsin, Madison, have shown that proteins yield less available calories (after digestion) than either fats or carbohydrates. Burning protein in a bomb calorimeter (to measure the energy contained in foods) provides 5.65 calories, while only 4.0 calories are available after absorption. Values for fats are 9.4 and 8.9 calories, and carbohydrates are 4.1 and 4.0 calories. You lose nearly 30 percent of the energy from protein in digestion but only 2 percent from carbohydrates.

When trying to lose weight, increase your protein intake and reduce your carbohydrates. You will feel more full after eating, burn more calories to digest the meal, and alter your blood chemistry to favor fat burning.
[Am J Clin Nutr, 79: 899S-906S, 2004]