Don't Compensate by Eating More 

When you add exercise to your routine, you get hungry more often—especially when you work out every day. Dealing with that hunger can be an uphill battle, because there is often a little voice inside your head that says, "I can eat whatever I want because I exercised today."

That rationale makes sense. But if you are trying to lose weight with exercise, you need to achieve a specific calorie deficit at the end of the day. If you satisfy your post-exercise hunger with high-calorie foods or even with too much healthy food, you'll end up replacing all of the calories you burned. Then, your calorie deficit and your potential weight loss disappear.

Fix This Blunder: Before you start or change your workout program, determine your total daily expenditure. You can calculate it yourself or get a metabolic test performed by a professional such as a personal trainer or registered dietitian. When you begin your exercise program make sure that you only increase your food intake so that you still maintain a calorie deficit at the end of the day.

A deficit of 500 calories per day or 3500 calories per week should result in a one pound weight loss each week.

Avoid Lopsided Training

A good fitness schedule includes cardiovascular (aerobic) training, strength training, and flexibility work (stretching).1 This balanced workout program ensures that your body stays healthy and fit. But each of these three components also has weight loss benefits. If you skimp on one or two of them, you'll end up with a lopsided workout program and you won't reap the full weight loss rewards of your exercise sessions.

Fix This Blunder: Most weight loss workout programs include aerobic activity so it's unlikely that you'll have to add cardio. But you should also make sure that you do 2-3 days of strength training, as well. If time is an issue, do a circuit workout and complete short intervals of strength exercises between 5-10 minute bursts of cardio. Then, finish every workout with 10-15 minutes of stretching so that you maintain healthy joints and an injury-free body.

Don't Decrease Non-Exercise Physical Activity

It's great if you go to the gym every day and complete a killer workout—unless the payoff is that you spend the rest of the day on the couch. If you compensate for your workout by decreasing the amount of non-exercise physical activity that you do during the day, your total daily caloric expenditure may end up being the same as if you hadn't gone to the gym at all.

Fix This Blunder: Non-exercise activity thermogenesis (NEAT) should account for a significant percentage of the calories that you burn each day. NEAT is any physical activity that isn't intentional exercise: Walking around your home or workplace, cooking, even fidgeting. When your NEAT decreases, your metabolism slows, you don't burn as many calories2 each day and you don't lose weight.

If your workouts drain you to the point of exhaustion, it may be time to re-evaluate your program. Make sure that your high-intensity workouts are relatively short and that you include some easy recovery days during the week to give your body a chance to recuperate and rebuild.

Also, keep in mind that it's not always the workout that is causing the lack of NEAT. Sometimes the choice to lay on the couch or sit in a chair all day is made out of habit rather than genuine fatigue. Try to skip the afternoon nap and go for an energizing walk instead. Stuck at work? See if you can use a standing workstation or take short breaks to get out of your chair and move around.

Rethink Supplements and Sports Drinks

Do you refuel during or after your workout with sports drinks or bars? If so, you're probably erasing the calorie deficit that you just earned.3 In some cases, athletes need sports drinks, but for most exercisers, water is the best choice for hydration. And your post-workout diet supplement is probably not helping either. There are hundreds of products on the market and, sadly, most of them do nothing but make empty promises and drain your wallet.

Fix This Blunder: Instead of investing in bars, drinks, or supplements, invest in a visit with an accredited sports nutritionist or registered dietitian. They will help you to make sure you are getting enough of the right kind of calories to recover adequately from your workout. They can also help you to decode and perhaps debunk the claims of the supplement that you want to use.

A Word From Verywell

Regardless of your size, exercise should always be a part of your daily routine. You'll experience countless health benefits if you participate in physical activity every day. But if you are engaging in a workout program specifically to lose weight you need to be especially careful to optimize your plan to meet that goal. Make just a few small adjustments, avoid these common mistakes, and you're more likely to see the results on the scale.