Calories can be unkind. You can sweat for 30 minutes on the treadmill and burn off roughly 200 to 300 depending on your weight (larger bodies burn more calories during exercise). But nosh on a couple of cookies or sneak a second helping at dinner and you're back to square one.
If you're trying to lose weight - or prevent the pounds from creeping on - calories can easily sabotage your diet on a daily basis.
But here's the good news: The best way to win the battle of the bulge does not involve following a strict diet. Experts agree all it takes is making small changes, ones as simple as shaving off 100 calories a day.
If you want to lose weight permanently this year, you need to start focusing on what you'll have to do to maintain your goal weight. In other words, what will "forever" look like?
Let's face it, we are all pretty good at losing weight. But we're not so hot at keeping those pounds off. Eventually old habits - and calories - slip back.
In fact, data show that most people are gaining weight gradually over time, with the average North American adult putting on one to two pounds each year.
Based on this observation, obesity researchers view weight loss in two parts: the changes you must make to take weight off (e.g. cut 500 calories a day to lose a pound a week); and the changes you need to make to maintain your weight goal. If you understand now what you will need to do maintain your loss - how many calories you need to trim from your lifestyle - chances are you won't gain it back.
It's a forward-thinking perspective that's well worth considering - especially if you have a history of yo-yo dieting. Instead of focusing solely on how many calories you need to cut to drop weight, know too the calorie adjustments required to maintain that loss.
It's what researchers call the "energy gap." Simply put, the energy gap is the difference in calorie intake and calorie expenditure that's required to prevent gaining weight or to maintain weight loss.
To maintain a 10-per-cent loss of body weight, you need to cut 200 calories a day. For example, a 220-pound man will have to adjust his lifestyle by 200 calories to hold steady at 198 pounds.
That's because maintaining a body weight of 198 pounds compared with 220 takes roughly 200 fewer calories daily.
Maintaining a 15-per-cent weight loss requires a daily energy gap of 300 calories.
You may not need to lose weight but instead want to halt that middle-aged spread. To prevent weight gain, regardless of your current body weight, experts estimate you need to drop 100 calories a day by eating less, exercising more or a combination of the two.
Reducing your daily calorie intake is easier than you think. Making smart food substitutions and reducing portion sizes can make a big difference over time.
When it comes to exercise, walking 2,000 steps, jogging for 10 minutes, swimming for 15 minutes and pedalling a stationary bike for 12 minutes all burn roughly 100 calories.
As simple as it sounds, there is one hitch: you need to keep up those small changes to succeed at weight control. Be consistent and eventually those small changes will become automatic. Practice one - or more - of the following calorie-cutting tips to get you started.
Eat half of a medium-sized bagel instead a whole bagel. Save 142 calories.
Eat one medium orange instead of drinking 12 ounces of orange juice. Save 106 calories.
Pour 1/2 cup of granola into a small mug rather than one cup into a bowl. Save 200 calories.
Make an omelette with four egg whites instead of two whole eggs. Save 87 calories.
Top pancakes or waffles with 1/2 cup of berries and 1/2 low-fat yogurt instead of 1/4 cup of syrup. Save 125 calories.
Replace four slices of regular bacon with four slices of back bacon. Save 122 calories.
Lunch and dinner
Skip the cheese on your turkey or ham sandwich. Save 115 calories.
Spread your bread with mustard instead of one tablespoon of regular mayonnaise. Save 90 calories.
Order pizza with thin crust instead of deep dish crust. For two medium slices, save 120 calories.
Serve your pasta with tomato sauce instead of creamy Alfredo sauce. For 1/2 cup, save 130 calories.
Remove the skin from chicken before eating. For a five-ounce serving, save 50 calories.
Cut an eight-ounce steak in half and save one portion for another meal. For a New York strip loin, save 300 calories.
Top a baked potato with plain non-fat yogurt and salsa instead of regular sour cream. For 1/3 cup, save 100 calories.
Reduce your portion of cooked rice or pasta by 1/2 cup. Save 100 calories.
Enjoy your salad without croutons. For 1/3 cup, save 60 calories.
Squeeze lemon juice over cooked vegetables instead of adding butter. For each tablespoon, save 100 calories.
Use low-sodium vegetable or chicken stock instead of oil when sautéing. For each tablespoon, save 120 calories.
Replace 14 potato chips with two cups of plain air-popped popcorn. Save 90 calories.
Munch on 1/2 cup of fresh grapes instead of 1/2 cup of raisins. Save 150 calories.
Dip eight celery sticks into hummus instead of two flat-bread (lavash) crackers. Save 92 calories.
Say no to buttery topping at the movie theatre. For a large popcorn, save 300 calories.
Replace rich ice cream with frozen sorbet. For 1/2 cup, save 140 calories.
In coffee, use 2-per-cent milk instead of half and half (10-per-cent milk fat). For 1/4 cup, save 80 calories.
Order a latte (12 ounces or "tall") with skim milk instead of whole milk. Save 90 calories.
When thirsty, drink a glass of water instead of fruit juice. For eight ounces, save 120 calories.
On the weekend, drink two light beers instead of two regular beers. Save 100 calories.
When buying regular soft drinks, share a 20-ounce serving or save half for another day. Save 130 calories.
Leslie Beck, a Toronto-based dietitian at the Medcan Clinic, is on CTV's Canada AM every Wednesday. Her website is lesliebeck.com.