Fad Diets


An Interview with Sangita Phadtare, Ph.D

(Spring 2013)more conversations

Recently it seems that a new diet appears every few months.  What's going on? 

CDC (Centers for disease control and prevention) data suggests that obesity has been on the rise for past couple of decades in the US. The weight loss diets have thus become a thriving industry. There are several factors why a particular diet may not work for someone or why they may not adhere to it for a prolonged time. Thus, people are always looking for something that works. This leads to new diets appearing on the market all the time.

The Mediterranean Diet has been around for some time.  Why do some diets come and go quickly and others remain?

Key to the success of any diet is long term adherence. This depends on various factors such as, (i) how flexible the diet is, (ii) if it is affordable for long term use, (iii) if the long term use of this diet is safe with respect to overall health and (iv) how effective it is for weight loss for that particular person. The Mediterranean diet allows one a wide variety of food items, it restricts the frequency with which you can eat it. Therefore, some foods are allowed daily, some are allowed weekly and foods like red meat are allowed once a month. This allows the user to enjoy various foods and does not make him/her feel deprived. So they are more likely to continue the diet. This diet has a good balance of protein, carbohydrate and fat as well as vitamins, minerals and fiber. Recent studies have shown that following this diet may be linked to reducing the incidence of coronary heart disease. As the diet allows a variety of foods, a person can choose based on what they can afford. This may be the reason why this diet has been around for some time.

It often seems difficult to separate a diet from the media attention it garners.  Aren't new diets just ways to make money through the sale of books and related food products?

Several times that is indeed the case. Not all the diets have been evaluated for their long term effect on overall health. Some of these diets are endorsed by celebrities and people thus start following them without giving much thought to long-term effects.

How best can the average consumer evaluate a new diet? What are the dangers of starting a new diet? 

A diet should include at least some amount of all the three macronutrients-carbohydrates, proteins and fats. For example, there should be at least 100g-150g of carbohydrate per day in the diet. Vegetarian people should get the protein from different sources to make sure that they get all the essential amino acids. Also, the consumers should make sure that they are meeting the daily requirement of vitamins, minerals and fiber. It should be noted that fiber comes mostly from the plant sources and does not contribute to our caloric intake. However, it is important for the health of our digestive apparatus. Some of the so called ‘fad’ diets do not meet these criteria and lead to severe health problems. For example, a diet severely lacking in carbohydrate and protein will lead to breaking down of the muscle protein to maintain the blood glucose level. A diet completely devoid of fat will lead to deficiency of fat soluble vitamins like vitamin A, D, E and K. Even though these vitamins are present in the diet, they need dietary fat for their absorption. Also omega-3 and omega-6 are the fatty acids that can be obtained only through diet. A diet devoid of fat will lead to their deficiency and serious health consequences as a result of that.

Are there any examples of popular diets that have caused harm to consumers?

Atkins diet is one of the popular diets and works well for most. However, there is lot of debate regarding this diet. As it is a low carbohydrate diet, its induction phase especially may lead to mild ketosis and also may be low in fiber.

The Paleo Diet has been quite popular recently.  What is it and why is it so controversial?

The paleo diet, short for paleolithic diet, is also referred to as the caveman diet or hunter-gatherer diet. It is based on the presumed ancient diet consumed during the Paleolithic era, before the advent of farming and thus inclusion of grains in our diet. It consists mainly of fish, meats, eggs, vegetables, fruit, and nuts. It does not include grains, legumes, dairy products, potatoes, refined and processed foods. Its supporters claim that our genetic makeup has not changed since the dawn of agriculture and we are genetically adapted to the diet of our Paleolithic ancestors. Thus, this is an ideal diet for human health. Its distractors however categorize it as a fad diet and argue that the ancestors had reduced calories in their diet, had shorter lifespans and did not have factors arising due to civilization influencing their health. So what may have been ideal for the ancestors may not be ideal in the present day scenario. Research also suggests that these ancestors may have suffered from diseases like heart disease or cancer, so the diet did not confer protection against these diseases.  

A recent entry in the dieting arena is the Fast Diet.  What is it and why is it suddenly so popular?

The fast diet includes intermittent fasting. They say that using this approach for most of the time, you can eat what you like, and get slimmer and healthier as you do it. By reducing your calorie intake for two days a week (500 calories for women, 600 for men) you’ll lose weight and enjoy a wide range of health benefits. It is the so called “5:2” regimen, severe calorie restriction for two days a week and normal eating the other five days. Dr. Michael J. Mosley is mainly responsible for popularizing this diet. He was featured in a BBC2 Horizon documentary Eat, Fast & Live Longer in 2012.This diet is labeled as a ‘fad diet’ and people are cautioned that there is no evidence that the diet meets its claimed benefits and that little is known about whether it could be harmful to health in the long-term.

I've often heard that eating a good mix of foods in moderation is the best diet? Is that true?

Yes, variety in food is very important. For a healthy person, who has no genetic/physiological predispositions with respect to obesity, calories in and calories out is the principle that works best. This means if your caloric intake is equal to your caloric output, you should maintain weight. If you eat more calories than what you expend, then it will lead to positive energy balance, meaning weight gain and if you eat less number of calories than what you expend, you will lose weight. As discussed above, you should include a balanced mix of carbohydrates, proteins and fats in your diet along with vitamins, minerals and fiber, drink enough water and supplement this with some physical activity every day. Mixing and matching different types of food from different food groups such as grains, fruits, vegetables, meats, dairy etc will help you achieve a nutrient balance. Note that the most of the calories come from proteins, carbohydrates and fats, fat being the most energy dense nutrient. The general recommendation is that about 45-65% of our caloric intake can be from carbohydrate, 10-35% from proteins and 20-30% from fat. Fiber should be ~38 g for men and ~25 g for women per day. As mentioned above, fiber mostly comes from plant sources and does not contribute significantly towards calories.

Sangita Phadtare, Ph.D is an Associate Professor, Department of Biochemistry and Molecular Biology at Robert Wood Johnson Medical School. She is the Course Director for the Medical Biochemistry course taught to the first year Physician Assistant students and Co-Course director for the GI-Metabolism-Nutrition course taught to the RWJMS-first year medical students. Dr. Phadtare teaches biochemistry and nutrition. Contact: Sangita Phadtare, Ph.D phadtasa@rwjms.rutgers.edu



Paleo Diet

Fast Diet

Mediterranean Diet - New York Times article

- InfoPOEM