5 Diet Myths Debunked

By Stephen T. Sinatra, M.D., F.A.C.C., F.A.C.N., C.N.S., C.B.T.

Have you resolved to lose weight in 2020? Join the club. Getting in shape and/or losing weight are consistently the top New Year’s resolutions every year. On one hand, I applaud and encourage everyone’s desire and motivation to make the new year a healthier one. But on the other hand, research finds that most people give up on their goals by February! I can certainly understand why. There are so many weight loss and diet myths out there, it’s hard to know what will actually work.

If your goal is to lose weight this year, I’d like to help you succeed by setting the record straight on five of the biggest diet myths:

Diet Myth #1: Eating Fat Makes You Fat

Considering 1 gram of fat has 9 calories, while 1 gram of protein or carbohydrates has 4 calories, it kind of makes sense that if you want to lose weight, you should eat less fat. But research shows that cutting fat out of the diet doesn’t help you lose weight at all. After decades of dutifully following low-fat diets for not only weight loss but also heart health, Americans were becoming fatter than ever.

Why the rise in obesity? Low-fat diets tend to be much higher in sugar and carbohydrates (which are converted to sugar). The body responds to this sugar overload by churning out insulin, a hormone responsible for moving sugar (glucose) into cells for energy. Any excess sugar not moved into cells is stored as…fat. Multiply this by three low-fat, high-carb meals a day (not to mention snacks), that’s a lot of extra sugar being stored as fat.

It didn’t take long for researchers to start questioning the supposed benefits of reducing fat. According to a Harvard meta-analysis:

“Diets high in fat do not account for the high prevalence of excess body fat in Western countries; reductions in the percentage of energy from fat will have no important benefits and could further exacerbate this problem. The emphasis on total fat reduction has been a serious distraction in efforts to control obesity and improve health in general.”

Know there are several types of dietary fat, some better for you than others. Unsaturated fats are naturally occurring fats typically found in whole foods like avocados, fish, olives, seeds, and nuts. Certain unsaturated fats like omega-3s are very beneficial to your health and even play a role in weight loss and building muscle.

And contrary to popular belief, saturated fats like a nice juicy steak and whole-fat dairy can be enjoyed in moderation without worrying too much about weight gain. Believe it or not, saturated fat actually has important heath-enhancing properties. It helps promote satiety so you don’t overeat. It is a component of cells, giving them stiffness and integrity. It helps the body absorb and digest many different nutrients. And it even protects bones, bolsters immunity, and lowers Lp(a), a substance in the blood that increases risk of heart disease. (As a cardiologist, I would be remiss if I didn’t mention that saturated fat’s link to heart disease has been widely debunked.)

Trans fatty acids (or trans fats), on the other hand, were developed in a lab to help prolong the stability and shelf life of processed foods. These fats have absolutely no nutritional value, and they do affect overall health and waistlines. Trans fats should be eliminated from the diet.

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Bottom line: Unsaturated and saturated dietary fats don’t make you fat. Sugar and trans fats do. Avoid both like the plague.

Diet Myth #2: Artificial Sweeteners are a Useful Weight Loss Aid

Speaking of sugar, replacing it with calorie-free artificial sweeteners like aspartame (Equal), sucralose (Splenda), or saccharin (Sweet ’N Low) makes sense for weight loss, right?

Interestingly, no…research is finding that sugar substitutes can hinder weight loss. In a large-scale study of 5,158 adults followed for 10 years, those who drank 21 or more diet sodas per week had double the risk of becoming overweight or obese compared to nondrinkers.

Here’s why: Your body responds to artificial sweeteners much the same way it responds to real sugar. Artificial sweeteners activate your taste receptors. In turn, your body releases insulin, in anticipation of moving sugar (glucose) into the cells for energy. But because artificial sweeteners don’t contain actual sugar, the insulin ends up removing whatever small amount of sugar is already in the blood, causing glucose levels to dip too low and triggering hunger.

The body also releases hunger-related hormones—those that tell the brain “I’m hungry, go eat” and “I’m full, stop eating.” But again, since artificial sweeteners deliver no calories, the “I’m full” message never gets delivered to the brain, so you continue to feel hungry and eat.

One study found that all this occurs because artificial sweeteners negatively alter the way gut microbiota (friendly, health-enhancing microbes) respond to blood sugar.

On a related note, other chemicals in foods called obesogens are actually linked to weight gain, further strengthening the argument that natural is better.

Bottom line: If you’re trying to lose weight, limit or eliminate your intake of artificial sweeteners. Try to get used to things being less sweet, and rely on small amounts of natural sweeteners with nutritional benefits like raw honey and pure maple syrup. If you must use a sugar substitute, try xylitol or stevia, both of which are made by nature and don’t mess with your blood sugar or gut bacteria the way lab-made sweeteners do. (In fact, stevia aids in glucose control, making it an excellent choice for people with diabetes.) If you do use xylitol, please note that it is very toxic to dogs, so be sure to keep it out of paws’ reach.

Diet Myth #3: If You Exercise, Diet Doesn’t Matter

Many people believe if they work out, they can afford to eat whatever they want. Don’t fall into this trap, folks – this kind of thinking can sabotage any weight loss plan.

Part of the problem lies with the fact that people overestimate the number of calories they think they burn while exercising. One study found that moderately active, normal weight people assume they burn 3-4 times more calories than they actually do.

To compound the problem, research has shown that people also dramatically underestimate the number of calories they consume.

The typical person really doesn’t burn that many calories during a workout session. (Professional or elite athletes or those engaged in heavy-duty training for an athletic competition are a different story.) On average, an hour-long jog expends about 400 calories. That may seem like a lot…until you realize that a grande Frappuccino contains 400 calories. Think about that: One sugary coffee drink cancels out an hour of exercise.

Bottom line: Exercise is extremely important. It improves heart health, protects against countless diseases, alleviates depression and anxiety, builds muscle and enhances your physical appearance, and increases longevity. You should be physically active every day. But no amount of exercise can “cancel out” a consistently poor diet. When it comes to weight loss, decreasing calories and maintaining a healthy diet actually matter more than exercise.

Diet Myth #4: Go Gluten-Free to Lose Weight

Gluten is the name of a protein found in wheat, durum, rye, barley, semolina, and various other grains. It acts like glue, helping food to maintain its shape.

Certain people with a condition called celiac disease are allergic to gluten, causing symptoms from abdominal pain and bloating, chronic diarrhea, and weight loss to fatigue, joint pain, and malabsorption. Others still have gluten sensitivity, which is less severe than celiac but still leads to bloating and other digestive symptoms. For these people, eliminating gluten-containing foods can be life changing.

Celiac disease aside, the nation seems to be ga-ga for gluten free these days. It’s become one of the hottest trends. But does it help the average person lose weight?

Research indicates this is yet another diet myth. Even though data suggest that 65% of Americans choose gluten-free products because they believe they are healthier, a review article published in 2015 concluded that, “Despite the health claims for gluten-free eating, no published experimental evidence supports weight-loss with a gluten-free diet or suggests that the general population would benefit from avoiding gluten.”

Look – with gluten-free, a carb is a carb is a carb. If you go on a gluten free diet and eat a lot of simple carbohydrates that happen to be gluten free, you’re not going to lose any weight, just like you wouldn’t lose weight by eating lots of carbs with gluten. If you cut out the carbs, and eat mostly fresh fruits and vegetables and some healthy proteins, you’ll likely lose weight, gluten or no gluten. With that said, adding gluten-free grains to your diet isn’t a bad idea. Whole grains such as amaranth, buckwheat, millet, and rice are great sources of fiber, protein, B vitamins, and iron. And being so high in fiber, they help to fill you up and keep you full for longer periods of time, which helps prevent overeating. Some gluten free products offer less refined alternatives which are – hands down – healthier than processed foods.

Bottom line: Gluten-free living may not be the most effective weight loss tool unless you limit your carbs, but gluten-free whole grains can still make wonderful additions to your diet.

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Diet Myth #5: Eating Healthy Is Too Expensive

 I hear this diet myth all the time. But eating healthy can cost way less than you think. Here are some tips to get the most bang for your buck:

  • Buy in-season produce. Fresh produce that’s in season is always cheaper. Stock up and freeze a bunch of it. Or simply buy frozen vegetables, which have nearly the exact same nutritional value as fresh.
  • Know when to choose organic. While eating organic is preferable to conventionally grown varieties, you don’t need to buy everything organic. Certain fruits and veggies are worse than others when it comes to pesticide residue.
  • Vegetables are generally less expensive than meats and poultry.
  • Plan your meals around sales at your grocery store.
  • Try less expensive cuts of meat. Chicken thighs, for instance, cost less than breasts. Bone-in is cheaper than boneless, too. I still recommend splurging on organic or grass fed, but less is more with meat. Better to fill up on fresh vegetables, salads, fruits, nuts, seeds, and beans, most all of which generally cost less than meat.
  • Buy in bulk. This is especially cost-effective when shopping for coffee beans, grains, nuts, and seeds.
  • Stop buying junk food. You’d be shocked to see how much the chips, pretzels, ice cream, cookies, pastries, and sodas cost you. By getting rid of these items, you can spend more of your hard-earned money on higher quality foods.

Bottom line: You don’t have to break the bank to eat well. With a little planning and discipline, anyone can do it. Besides, if eating healthy can help keep you well, isn’t it worth it in the long run?


© 2017, 2019 Stephen Sinatra, MD. All rights reserved.

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  1. Tammy

    on January 3, 2019 at 12:39 pm

    Thank you for this. I have a myriad of autoimmune issues I’ve been working to lesson with diet. One of them is not diabetes, however, I’m very affected by gluten, sugar and other grains. Inflammation goes way up by consuming these foods, and I’ve been diagnosed with SIBO as well. Such is the puzzle of the affects of diet. My spouse is stuck in the 80s and still thinks fat, of any kind, is bad. Hopefully your article will help to re-educate him. And hopefully this will re-educate people on gluten. The latter is frustrating for those of us needing to avoid, especially when trying to eat out anywhere. All education can only be good! Thanks so much.

  2. LC

    on January 6, 2020 at 10:08 am

    First, thank you for all you do! So wonderful to have an MD and cardiologist talk about the limits of drugs and the importance of a natural diet. Wheat is problematic on 4 levels: most wheat is GMO, gluten content 10 times higher than it was when we were kids in the 60’s, high glycemic index and LOADED with Monsanto’s glyphosate since 1975(which disables the digestive system of the bug and has contaminated oats, corn, soy as well). After reading “Wheat Belly” and “Grain Brain”, I am off wheat forever (happy digestion now). Since I don’t eat grains, added sweetners, trans fats or Omega 6 seed oils, it is almost impossible to stop losing weight, and I eat all day.
    Logical to think that wheat is good to eat, since it has been around for thousands of years (but only 4% of human history), but Big Agriculture has poisoned us and (farmland soil) slowly via this “trust worthy” food.

  3. Jorgen

    on January 6, 2020 at 11:52 am

    I’m diabetic if I don’t control my diet by limiting carbohydrate intake. I don’t use medication but instead keep the net carbohydrate intake to around 80-120 grams/day. I drink “diet” drinks with artificial sweeteners but I don’t experience the craving of other sweets after consuming “diet” drinks often described by nutritionists. However, if I eat a candy or two containing sugar I find it difficult to stop as I crave more. I should add that prior to being a diabetic I wasn’t a soda drinker but ate a lot of carbohydrates and avoided fat. I now consume 60-70% of calories as fat, and the other 30 -40% are split equally between protein and carbohydrates. Obviously there are daily differences but they aren’t big.
    This diet make up has helped me control diabetes, and it allows me to consume 600+ grams of vegetables and fruit daily. I don’t eliminate any food group but I eat refined carbohydrates and potatoes sparingly. I just learned to use chayote in place of potatoes.
    Recently I started intermittent fasting on the 16:8 system, and if I wasn’t already a fat burner I don’t think it would have been possible. Prior to changing my diet four years ago I had to eat constantly and immediately after waking in the morning.
    Many thanks for the newsletters, very often they bring new ideas to me.

  4. Jorgen

    on January 7, 2020 at 2:00 pm

    Please allow me to make a correction to LC’s comments on wheat. GMO wheat isn’t commercially grown in the USA. Corn and soy is a different story as it is virtually impossible to find commercial quantities of non-GMO soy and corn.

    Gluten which is the protein in wheat and therefore in wheat flour has decreased over the years. In the late 70’s and early 80’s high gluten flour with a 14-15% protein content existed. Not so anymore, note that hi gluten flour is a typical 70% extraction and not a whole wheat flour which typically is higher in protein content but the protein is of lower baking quality.

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