Why Can’t I Lose Weight

Have you been struggling with weight  loss? Maybe you went on a diet and successfully lost 10 lbs, but then gained it back. Do you continuously  try to change your habits and still can’t lose any weight? A basic  understanding of metabolism and the science behind weight loss may help you get on track.


You may have heard people talk about their “metabolism”. Some people say they have a fast metabolism and that is why they stay skinny. Others say they have a slow metabolism which is why they can’t lose weight. It is true that everyone’s metabolism is different; however, you do have the ability to impact your metabolism by what you do daily and how you behave.

Everyone has what is called a BMR or “basic metabolic rate“. This is how many calories you burn in a 24 hour period if you were to do no physical activity. For example, if you laid in bed all day and did nothing, you would burn this many calories just to breathe, digest your food, keep your heart beating, etc. The only way to know what this rate is for sure is to be hooked up to a machine that calculates how much carbon dioxide you exhale over a certain time period in order to tell how many calories you are using, and then extrapolating that data out into a 24 hour period. This expensive test obviously is not feasible for everyone, so there are many calculations that Dietitians or Nutritionists use to estimate calorie needs. These calculations are based on height, weight, sex,  age, physical activity level or other variables.

Low Calorie Diets

In order to lose weight, the goal is to consume less calories than your current BMR (basal metabolic rate) plus any additional physical activities you do each day. For example, if your BMR is 1500 calories, which may be the case if you were an average-sized female, if you ate approximately 1500 calories that day and did little to no physical activity, you would maintain your weight. However, if you ate 1200 calories that day, you would create a deficit of 300 calories. One pound of fat is approximately 3000 calories, so you might lose a pound in about 10 days. Clearly the greater the deficit you create, the more weight you will lose; however, there are some caveats to this rule. In order to provide your body with the nutrients you need to feel good and be able to perform your daily activities, you need to at least eat 80-90% of the calories present in your BMR. As a general rule, never go below 1200 calories unless you are a very small person or under a physician’s guidance.

In order to lose weight faster, you can add physical activity to your routine, but
remember that you didn’t pack on the pounds in just a few months, so it is not realistic to lose them again that quickly. Also, you may be able to join a low calorie weight loss program. Some physicians have “Physician Supervised Weight Loss” programs in which they prescribe very low calorie regimens, maybe even below 1200 calories, but with appropriate lab tests and supplements to make sure your body gets what it needs. Some physicians even have programs under which you are prescribed a mostly liquid diet in order to meet your nutrient needs and lose weight at the same time.

Low Carb Diets

Low Carbohydrate Diets, sometimes referred to as “Low Carb” diets, are another popular approach to weight loss. Food consists of three major nutrients: Protein, Fat, and Carbohydrate. Carbohydrates make your muscles work and perform physical activity. They also are the preferred source of nutrition for your brain. Carbs are necessary for you to live and perform your daily functions – the debate is over how much is the minimum necessary. Some research has shown that the brain requires approximately 120 grams of carbs daily – the equivalent of about 4 cups of mashed potatoes or 8 slices of bread, for example – in order to function properly. If your brain does not have enough carbs, it runs on a substance called “ketones” which are a byproduct of fat metabolism.

Even though carbs are important for daily function, that is not to say that cutting carbs in your diet won’t help with weight loss. Most people eat well more than 120 grams of carbs daily, the minimum needed for adequate brain function.

Cutting back on your carbohydrates may help you to lose weight because it would cut down on your calories. Make sure that you are also eating the right type of carbohydrates like fruits, whole grains, and vegetables, and the right portion sizes, rather than sugary foods, desserts, or sweetened beverages. High-calorie sugar-sweetened items like cakes and cookies can pack a big calorie punch. A small little debbie cake can hold 400 calories, which can squash your weight loss efforts for the day.

Low Fat Diets

Low Fat diets have come out of the limelight as a healthy weight loss technique recently, and are usually only pushed for those suffering from heart disease and other cardiac conditions. Low Fat diets may not be effective in weight loss because usually they cause a person to overcompensate with carbohydrates and thus does not lead to a calorie deficit. It is usually more advisable to consume a diet with the right amount of healthy fats rather than a low amount of fats in general. Omega-3 Fatty Acids or other Essential Fatty Acids can help control your cholesterol and lead to a healthy heart. These fats are present in nuts, avocados, olives, olive oil, canola oil, and other oils.

Avoiding Saturated Fats such as butter, cream, whole milk, and fatty meats like hamburger meat can make your heart healthier and also contribute to weight maintenance. Even though it is healthy to consume fats, avoid excessive amounts of fats that might be present in fried foods or foods cooked with excess oil. The Dietary Guidelines recommend that fat be around 30% of your calories, which for your average 1500 calorie diet, would be around 12-13 teaspoons of oil daily. Fat adds up quickly and can add up to a large amount of calories, so even with your healthy unsaturated fats, use them sparingly.


Diet alone can create a calorie deficit for weight loss, but it usually not enough to give you the faster weight loss you are looking for. Exercise can fill in the blank between meeting your nutrient needs but still producing a calorie deficit. For example, if you burn 300 calories a day, and eat 300 fewer calories than your BMR, you would have a calorie deficit of 600 calories which would cause 1 pound of weight loss in 5 days, a more effective weight loss. Exercise is also important for heart health and longevity.

Cardiovascular Exercise

Many articles and books state that a slower pace and a lower heart rate is more effective for weight loss. While it is true that slower paces burn more fat than carbohydrates, it does not burn as many calories overall as a faster pace of exercise, which is what matters for weight loss. A faster pace of exercise, often called “cardio”, short for “cardiovascular”, is the most heart healthy, but burn mostly carbohydrates. This might make you hungrier and  overcompensate by eating more carbohydrates. Despite this, it is still the best option for weight loss if you stick to your diet prescription because weight loss is based on calories in vs. calories out. Cardiovascular exercise is usually 70-80% of your Maximum Heart Rate. Maximum Heart Rate can be calculated by subtracting your age from 220. Thus a 25 year old’s maximum heart rate  would be 195 bpm. Good cardio exercise would keep your heart rate at about 135-156 bpm.

Resistance Training

Resistance Training, also referred to as weight training or strength training, is
also important for weight loss. While this type of exercise does not burn many calories while you are doing it, it
builds your muscles. It is proven that those with more muscle mass have higher basal metabolic rates, and thus burn more calories in a 24 hour period, even if they don’t exercise that day. You can think of it like interest on an investment – if you build up the muscle mass, it will pay you back in the long run by boosting your metabolism.

Interval Training

Perhaps the best way to lose weight is interval training. This combines short bursts of carbohydrate-burning high intensity physical activity with longer periods of fat-burning medium or low intensity physical activity. Thus you are burning a good balance of fuel sources along with burning more calories in general since long stretches of high intensity activity is difficult, especially for the beginner. One way to interval train is to get your heart rate in the low end of the cardiovascular range for about 5 minutes, and then sprint for 1 minute and get your heart rate to about 90% of maximum. Continue to repeat this for a great weight loss effect because this will burn many more calories than cardiovascular exercise alone.

Diet Pills

Over the years, the FDA has approved a number of diet pills to assist with weight loss. This is often used to “jump-start” a weight loss regimen. Keep in mind that if you do use diet pills, they are not without risks, so speak with your physician about the risks that each specific diet pill comes with. Also keep in mind that there is no magic bullet: each prescription must be used along with a healthy lifestyle including diet and exercise routine. You really need to change your life in order to lose weight, and no diet pill is going to change that. There are a few different types of diet pills.

Appetite supressants are just as they sound: they suppress, or reign in your appetite so you are not as hungry and don’t eat as much. You can see, however, that if you were eating high calorie foods or sugar sweetened beverages that this would not work very well. Fat absorption inhibitors are another type of diet pill that actually doesn’t let fat get absorbed in your stomach. A common and unpleasant side effect for some people on this type of pill is diarrhea. Often times the weight loss results from the person being retrained not to eat fatty foods due to the unpleasant diarrhea it produces, thus leading to weight loss.

Herbal Supplements

Many Herbal Supplements claim to help with weight loss. Be careful with herbal supplements and be sure that you are dealing with reputable companies because they are not regulated by the FDA and may contain harmful compounds if you are not careful with the brand you select. Herbal supplements work in much the same way as diet pills, usually just to a lesser degree. Some herbs decrease your appetite and make you not as hungry, thus causing a calorie deficit and then weight loss. Others may decrease fat absorption. Just be sure to check with your doctor first, especially if you are taking other medications, to make sure they don’t interact.


Liposuction is a surgical procedure in which fat mass is removed from your body by a doctor with suctioning. This is generally not a technique used for large amounts of weight loss – most plastic surgeons will advocate for you to get in shape before this procedure, and use it just to get rid of stubborn fat or light layers of fat in undesirable places. People who lose a lot of weight also may have excess skin with a small layer of fat that needs to be removed in order for them to look like they’ve always been a normal weight. It is important for you to get in shape first and lose the weight you want to lose using the methods above before contacting a plastic surgeon and getting this procedure.

Gastric Surgery

There are several methods of gastric surgery that are highly effective for weight loss. Especially if you are morbidly obese, with a BMI over 40, consider these methods in order to lose large amounts of weight. Keep in mind that these surgeries are used in extreme cases only due to the high death rate that obesity causes. These surgeries are risky, and cause you to have a lifetime of dietary changes. You will not absorb food the way you used to after having one of these procedures, thus you will probably need chewable vitamins, minerals and protein supplements for the rest of your life. There are also certain food restrictions that you will also need to follow for the rest of your life. Check with your physician to see if this is an option for you. Even though you may have to change your habits significantly, it is always a good option if you have tried everything else, still can’t lose weight, and are facing multiple health problems due to your obesity. If you just want to lose a few pounds or even 10 or 20, you probably should try the diet and exercise techniques discussed above first to truly get the results you are looking for.