She was getting frustrated. I had seen it many times before. Her husband was losing more weight than she was, but they were doing virtually the same thing. It's one of the cruel realities of weight loss: Men tend to lose weight more easily than women. It's not fair, but understanding the reasons why can help you make progress.

It starts on a hormonal level. Women tend to have more of the hormone estrogen, which makes it easier to store fat. Fat is critical for childbirth, so women's bodies use that extra estrogen to hang onto fat more stubbornly than men.

The differences are significant. A woman is considered an athlete if she has a body-fat range from 13 to 20 percent. A male athlete's body-fat range is a much lower 5 to 13 percent.

Since women are more likely to be overweight than men, researchers decided to see if there was a difference in the speed of their metabolism. They took 114 men and 121 women and measured how many calories they burned over 24 hours. Then they adjusted the figures to account for such things as body weight, body composition, exercise and even the effects of the menstrual cycle. The results were stunning.

After "adjusting for differences in body composition, age, and activity," the researchers found that women burn approximately 5 to 10 percent fewer calories than equivalent men. A 5-percent difference means that if a man and a woman of the same weight and body composition both ate 2,000 calories a day for a month, the woman would hold onto nearly 1 pound more than the man. And that's just in one month!

There's a way to fight back. Start lifting weights.

One of the most common myths that women believe is if they lift weights they'll start to look like a man. In fact, unless they're taking artificial stimulants like testosterone, women will never build large malelike muscles. They'll grow stronger, but the muscles tend to develop as lean rather than bulky.

Building muscle mass is critical to long-term weight loss for women. The more muscle you have, the more calories your body burns. If a man and a woman weigh the same and they both go on a diet at the same time, men will lose weight faster because of their extra muscle. Women who use weights (or resistance exercises) build more muscle and drop the fat faster.

The differences between the sexes go deeper. On a cellular level, fat cells have hormone receptors. Those receptors can be alpha or beta receptors. Alpha receptors slow down the breakdown of fat while beta receptors speed it up.

Men tend to have more beta receptors in their abdominal region, so when they start on a diet their stomach will shrink faster than a woman's.

Then there are the psychological differences. Women are more likely to engage in "emotional eating" because it may be harder for them to suppress the cravings.

Researchers at Brookhaven National Laboratory decided to conduct a brain-imaging study to see how men and women responded to their favorite foods. When presented with things they liked, brains of both men and women "lit up" in areas associated with conditioning, emotional regulation and motivation.

Then researchers asked them to inhibit their response to food. In other words, use willpower to suppress the cravings. Both men and women reported back that they were less interested in the food and less hungry.

But only the men showed a decrease of activity in those food-activated brain regions. Even though women said they were less hungry, the areas of their brains that control the drive to eat were still firing away.

Deal with it by keeping a mood journal. See if you're eating for emotional reasons or if you're really hungry.

The best way to deal with the differences is to stop comparing. If you're a woman, don't expect to lose weight as fast as a man. As long as fat loss (and muscle gain) is happening, you're making progress. Compete against yourself.

Caution: Before beginning any diet or exercise program, check with your health care professional first. For a free consultation with a trainer, call 305-296-3434. More articles are online at www.WeBeFit.com.