The holidays can wreak havoc on a diet. If it's not the temptations — the desserts and rich foods — then it's being out of your element, staying with relatives who don't exactly share your perspective on health.

I go back home to Philadelphia, which in any given year is ranked the fattest city in America, save for when San Antonio or Miami wants a piece of the pie.

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I did fight back the temptation this year to make a pilgrimage to South Philadelphia to Geno's Steaks, the basilica of the patron saint of cheesesteaks, and Pat's King of Steaks, the predella and tabernacle housing the unholy trinity: thinly sliced rib eye, Cheez Whiz and crusty Italian rolls.

What a pity, for I inadvertently overindulged on the healthiest items I found at my parents' house: nuts, pumpkin seeds, dried fruit and orange juice. I soon came to realize that some health food isn't healthy at all when you gorge yourself.

Healthy but Calorie-Dense

Dried fruit: What could be healthier than fruit? Well, not dried fruit. I was gulping down handfuls of dried figs and apricots, while deriding those feasting on cholesterol-ridden shrimp and a dip so laden with fat that it could serve as window caulking. The problem with dried fruit is that there's no water to fill you up; you'll quickly lose track of how many pieces of fruit you're actually eating. Each handful — and there were surely more than a dozen — contained 50 to 100 calories, meaning I easily consumed a Big Mac's worth of calories.

Nuts: Judging by the grease and salt on my hands, I was eating the grease-and-salt variety of mixed nuts. But even dry-roasted and unsalted nuts pack a lot of calories. While I scored on copper, magnesium and other essential minerals, I consumed nearly 900 calories from a cup of mixed nuts.

Pumpkin seeds: Again, I got some magnesium, along with good ol' manganese and phosphorus. But seeds tend to be more calorie dense than nuts, with a cup of store-bought roasted squash or pumpkin seed kernels weighing in at nearly 1,200 calories. Fortunately I roasted whole seeds, which have about 300 calories per cup. My other consolation is that I burned a good deal of calories smashing open the pumpkin and scooping out the seeds.

Orange juice: Orange juice isn't just for breakfast anymore, especially when I don't drink the 23 varieties of Coke or Pepsi at my parents' house or can't adjust to the crisp taste of Philadelphia tap water. I drank a couple glasses of orange juice through the day. And in doing so I chugged down about 120 calories per cup, more calories ounce for ounce than the aforementioned colas.

OK, that was about 2,000 calories, close to my daily allowance, and I hadn't had Thanksgiving dinner yet.

Substitute, Not Complement

The lesson here is that healthy foods are supposed to be a substitute in your diet, not a complement. Folks pour on the olive oil because it contains healthy fats, but they don't eliminate the unhealthy fats from red meats. Similarly, some people sprinkle ground flaxseed on just about everything because of the healthy omega-3 essential fatty acids. But fat has twice as many calories than protein or carbohydrates, so the carefree sprinkling can add up.

We wonder why we are gaining weight even though we are eating healthy foods. The answer lies in the calories, which don't lie. A calorie is a calorie.

So, in the end, I could have had a cheesesteak. (Yes, that's one word, for non-Philadelphian readers).

Oh well, there's always Christmas.