Do Fad Diets Work? A Pharmacist’s Take

One popular theme New Year’s Resolutions are centered around is the desire to lose weight.  Every new year sees gym memberships spike, with many people looking at the newest, ‘best’ diet to help them lose weight and become healthier. It’s all too easy to fall into the trap set by one of those popular “fad diets.” You know, the diets that promise quick weight loss and (sometimes) better overall health. I want to discuss the pros and cons of some of the more recent popular diet plans and then provide a final opinion. As always, if you’re thinking about starting a diet, it’s best to discuss a plan with your physician or healthcare provider to determine what’s best for you.


Idea/Purpose: This diet gained popularity more than ten years ago and has been promoted by both celebrities and the press. Unlike most of the other diets described in this article (with the exception of the ketogenic diet), the gluten-free diet came from medical necessity.  About 1% of the US population has Celiac disease and cannot consume gluten without documented negative health effects.

Gluten is a generic name for the proteins that are found in wheat products, rye, and barley. It helps bread hold its shape and texture. There are some misconceptions about what it means to stop eating gluten. People think they will be healthier and lose weight because going gluten-free is also going ‘carb-free.’ The issue with this? Going gluten-free is not the same as going carb-free—gluten-free foods still contain carbohydrates!

What it consists of: Starting a gluten-free diet means eliminating any food that may have gluten proteins. This includes most grains, like wheat, rye, and barley. People who follow a gluten-free diet cannot consume foods that are made with regular wheat flour. Regular beer has gluten and cannot be consumed by someone on a gluten-free diet. There are a lot of foods that surprisingly contain gluten, which makes it difficult to adhere to the diet. Checking ingredients is a must!

Gluten-Free Diet Pros and Cons

Pros: Some think that gluten can contribute to inflammatory processes and that by eliminating gluten, one might be able to potentially decrease inflammation in the body. This has not been fully proven or disproven. We’ll keep it on the ‘Pros’ side for now—if research proves this potential pro, it may be worth looking at going forward.

Cons: There is quite a bit of evidence that a gluten-free diet may be more harmful than beneficial. A 2017 study showed that people who had the lowest amount of gluten intake actually had a slightly higher unadjusted rate of heart disease than those with the highest gluten intake. A study from 2016 showed that gluten-free foods lack vital nutrients and vitamins like folate, vitamin B12, vitamin D, calcium, iron, magnesium, and fiber. A lack of these vitamins and minerals can create serious health problems. Nutrient deficiencies in people with Celiac have been so well-documented that people who have celiac often have a nutritionist on their healthcare team.

There has also been increasing concern over arsenic and heavy metal exposure with gluten-free diets. Increased levels of arsenic, mercury, lead, and cadmium have been found in the blood and urine of people with gluten-free diets. This may be due to an over-reliance on foods such as rice and seafood which may cause increased levels of certain heavy metals in the body.

Final Verdict? Not a good option. Unless you have health-related issues like Celiac or documented gluten intolerance, adopting a gluten-free diet is not beneficial and may do more harm than good.

Fad Diets on magazine covers. Two magazine racks filled with healthy eating tips.
If a diet sounds too good to be true, it probably is!

Paleolithic Diet:

Idea/Purpose: The Paleolithic diet (Paleo for short) has become popular in the last few years, but the idea of eating like our Stone Age ancestors first popped up around 1975. The idea behind the paleo diet is called the “discordance hypothesis,” and is based on the idea that our bodies are not equipped to deal with a modern diet. Paleo dieting looks at what is more “natural” for us to eat, simulating the diets of our hunter-gatherer ancestors. Proponents of the Paleo diet argue that it is healthier for us to eat this way, while opponents argue that this view may oversimplify the story of how humans actually adapted to changes in their diets once farming was introduced. Genetic research has shown that humans have actually evolved to develop an increased number of genes related to the breakdown of dietary starches.

What it Consists of: The Paleo diet primarily focuses on eating foods that would have been available during the time of hunter-gatherers. This means the diet is heavy on fruits, vegetables, nuts/seeds, and lean meats (primarily grass-fed animals or wild game).  Fish like salmon and mackerel are eaten to provide the beneficial Omega-3 fatty acids. Foods that were introduced when humans started farming are excluded from the diet, which includes grains like wheat, oat, barley, and legumes (beans and lentils). This also means that dairy products are eliminated from the diet, along with refined sugar, salt, potatoes, and all highly processed foods.

Paleo Diet Pros and Cons

Pros: The Paleo diet definitely has the potential to help you lose weight, but there are no clear long-term studies that examine its long-term effects. It has demonstrated some potential to help reduce the risk of cardiovascular disease and type 2 diabetes.

Cons: Despite the potential benefits, there are still some concerns about the Paleo diet. A critical absence of calcium comes with the absence of dairy. There is also a concern with the lack of whole grains and legumes, which are a good source of fiber and vitamins that are needed in most diets to stay healthy. The Paleo diet can also be costly as it eliminates some affordable foods and requires others that may be more expensive.

Final Verdict? Some potential. But you may be able to achieve the same effects with healthy moderation in your regular diet along with exercise.

Ketogenic Diet:

Idea/Purpose: The idea behind the ketogenic diet lies in the theory that getting your caloric intake from fat instead of carbs forces the body to use alternative pathways to create energy. Ideally, in the ketogenic diet, the body burns fat as its energy source, and the body, therefore, enters a state called “ketosis.” Science has shown that ketosis may have some brain-protecting benefits, and this type of diet is often used in patients with seizures that may not respond well to other medications.

What it consists of: The ketogenic diet focuses on a high-fat, low-carbohydrate regimen. A general rule of thumb is that fewer than 50 grams of carbohydrates (equal to less than 4 slices of bread!) are consumed per day. Doctors sometimes come up with a specific ratio of fat to carbs for the diets of specific patients.

Ketogenic Diet Pros and Cons

Pros: There is quite a bit of scientific evidence that shows how the ketogenic diet has been beneficial in seizure disorders. Some early studies suggest that there are also potential benefits for blood sugar control in people with diabetes and for general cardiovascular health.

In terms of weight loss, there are a few studies that compare weight loss between groups that used a very low-calorie ketogenic diet (VLCK) compared to a standardized low-calorie diet. Those on the VLCK consumed about 600-800 calories per day (daily recommended caloric intake is about 1500-2000 calories) for about 30-45 days before being switched to a balanced diet that included carbohydrates at daily caloric intakes of 1500-2250 calories.  Some evidence shows that the VLCK is more effective than a standardized low-calorie diet.

Cons: There are still a lot of concerns surrounding the ketogenic diet.  There is very little research to look into the long-term effects of this diet to determine if it is safe or effective in the long term for anything besides epilepsy. A diet low in carbohydrates and whole grains can have some negative health effects like constipation and headaches (among others). As I mentioned earlier, the diet’s focus on high-fat content foods, potentially unhealthy foods, and saturated fat combined with its limits on fruits, veggies, and grains (all of which can contain carbohydrates) raises concerns for long-term heart health.

Final Verdict? Some potential. But too little research on long-term health effects for those without epilepsy, and the high-fat content may be too risky to recommend this diet.

Intermittent Fasting:

Idea/Purpose: The idea behind intermittent fasting diets is that by restricting eating to certain times or restricting calories on certain days, people will take in fewer calories overall, resulting in weight loss. There is also the belief that depriving cells of calories may slow down the progression of some age-related diseases. It may be easier for some people to have an iron will for a certain amount of time during the day or during specific days of the week instead of eating more moderately all the time.

What it consists of: There are two variations to intermittent fasting. One version is that people eat very few calories on certain days and eat normally on all other days of the week (usually 2 days vs 5 days). The other version involves eating only during certain hours and skipping meals the rest of the day.

Intermittent Fasting Pros and Cons

Pros: Some studies have shown that fasting helps to decrease blood sugar levels, blood pressure, and cholesterol. Intermittent fasting has also been shown to help with weight loss.

Cons: Despite some of the short-term benefits of intermittent fasting, there is a definite need for longer and more comprehensive studies to look at some of the long-term effects. Opponents of the diet argue that shortening the eating window may make it more difficult to get the necessary vitamins and nutrients. This type of diet may be more difficult for athletes or those with highly active lifestyles to follow.

Final Verdict? Some Potential. But there is not enough research to support or discredit this diet. This may be an option for those with trouble changing their diet to be more moderate.

A breakfast aisle at Casey's Foods, next door to Oswald's.
Make sure to make food choices that fit into your diet. There are a lot of choices!

Mediterranean Diet:

Idea/Purpose: There is no singular Mediterranean diet because it is based on the eating patterns of the people who live in countries that border the Mediterranean Sea. The “diet” focuses on moderation of certain foods while avoiding others, but also centers around eating and enjoying meals with family and loved ones.

What it consists of: The Mediterranean diet focuses on plants and plant-based foods. Two staples of the diet are fruits and vegetables. Most versions of the Mediterranean diet recommend about 7-10 servings of fruits or vegetables each day. Whole grains are also a big part of the Mediterranean diet, including ancient grains like quinoa, amaranth, millet, and farro. The typical intake of whole grains in the diet usually hovers around 6 servings daily. Fish that are rich in Omega-3 fatty acids are also a staple in the diet. Most versions of the diet recommend eating grilled fish once or twice a week.

Poultry and eggs are eaten occasionally, while red meat is rarely eaten (about once a month). Red meat is usually lean cuts of meat and kept to small portion sizes (about the size of a deck of cards). Sausage, bacon, and other high-fat meats are mostly avoided, as are higher-fat dairy products. Olive oil or canola oil is used instead of butter or margarine, and herbs and spices are used instead of salt. Nuts and seeds are used as a garnish or a small snack because of their high fat content. The Mediterranean diet also emphasizes exercise and eating meals with family members.

Mediterranean Diet Pros and Cons

Pros: This diet has been backed up with a lot of research showing how beneficial it is. Research shows that it decreases the risk of heart disease and also lowers LDL (bad) cholesterol levels. One study that followed participants for 17 years showed that it decreased the risk of stroke, especially in women.

Cons: There are not many concerns about following a Mediterranean diet. One potential drawback is that it may be a bit more expensive to follow than a traditional diet. Fresh produce, whole grains, and fish may be more expensive than other foods. There have been no demonstrated negative health effects on this diet, unlike many of the newer diets. The Mediterranean diet may not be as quick to produce weight loss effects, but it has been shown to be a safe way to improve overall health.

Final Verdict? Definitely a good option! With no real drawbacks to following a balanced Mediterranean diet, this is a great option for those who want to get healthy, while still eating foods they enjoy. Exercising in tandem with the Mediterranean diet is a great way to lose weight at a healthy pace.

Choosing the Right Diet for You

There are a lot of diets out there; some of them are simply fads advertised as the latest and best way to lose weight while others promise extremely lofty health benefits. Many fad diets have little to no research behind their long-term safety and efficacy.  If you are looking into starting a diet, it is important that you talk with your doctor or another healthcare provider about the potential benefits and risks of the diet plans you’re considering. Weight loss and overall better health are great goals to have, but it is critical that you do it in a healthy and safe way.

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Written by Hannah, PharmD

Hannah started working for Oswald’s Pharmacy in 2018. Hannah is a pharmacist focused on service and pharmacy innovation.