Popular Diets: Pros, Cons and the Bottom Line

By: Annie Kay, MS, RDN, RYT

Why is what to eat so confusing? Seemingly opposite diets claim the scientific high ground. Science constantly evolves as we sift what’s true from what is not. Nutritional science is no exception.

The reason for the range of diets popular today may be found in our genes, and in genetic individuality. Each of the many diets you hear about may be ideal…for someone, based at least in part by their genetics. None of them, however, works for everyone. Different diets can have widely different effects from person to person. When you compare diets, the level of evidence tells you if the diet will do what it claims. Many diets today have flimsy science behind them, while a couple have strong evidence that they work.

Here are two popular diets currently dominating the airwaves. We give you the scoop on what these diets are, the pros, the cons and our advice if they are likely to lead to a healthier future for you.

Popular Diet #1: Whole30 Diet
What is it?
The Whole30 is a 30-day elimination diet, where you take a sabbatical from processed and packaged foods, beans and legumes, dairy products, all-natural sweeteners and all sugar, alcohol, all grains and starchy vegetables like white potatoes. This diet claims to reduce inflammation and address a wide range of symptoms (bloating, skin issues), conditions (hypertension, blood sugar) and diseases (diabetes, cardiovascular disease).

The Whole30 is a particularly strict Paleo-style diet which features foods that humans ate before the Paleolithic (meaning preagricultural) period. While the aim underlying the Paleo diet – to eat foods that humans are genetically designed to eat – makes sense, the quest has triggered a hot debate over just what Paleo men actually ate. We know, for example, that they didn’t eat Paleo PowerBars, bacon, hamburgers or many other modern Paleo delicacies being sold today.

Another trend underpinning Whole30 is the elimination diet. Elimination diets - when you take a break from particular foods with the aim of minimizing food sensitivities, and allergy and inflammatory symptoms - is a clinical approach used in digestive issues, with allergies and food intolerances.

What does the science say?
Eating a whole-foods plant-based diet is healthful, and this program, if followed closely, can be nutritionally adequate for many. Unfortunately, it’s a high-risk diet for nutritional inadequacy because most people over-eat meat and under-eat plants on the diet that the Whole 30 makes are unsubstantiated. There is good evidence that practicing a new habit for 30 days tends to make it stick. While this is a short-term diet, the idea is that once you eat this way for a month, you’ll keep some of the healthful eating going.

Pros: Who might benefit and how?
• If you do have a food sensitivity, allergy or intolerance, you will feel better when you eliminate that food.
• It focuses on food quality.
• There is simplicity to the challenge, which for many is oddly easier than making ongoing healthful choices.

Cons: What to be aware of
• If you have a history of eating disorders or have an emotional component to eating - and most people do - Whole30 can be a deprivation diet and can launch bingedeprivation cycles.
• Whole30 is hard to do. It’s socially isolating and takes a large amount of time for food prep. It can be expensive. If you have struggled with sticking with a diet, or don’t like to spend time in your kitchen, this one may not be for you.
• It sounds like a quick fix. It’s not. Whole30 is a short-term diet-what matters more for your weight and your health are the choices you make regularly over the long term.
• A panel of expert reviewers for US News and World Report called it “the worst of the worst – nonsensical and over-restrictive”.

Are there no positive reviews from panel of experts or others?
The Bottom Line: If you think you might have food-related symptoms, are interested in trying an elimination diet, and are up for a diet that requires lots of prep, this one may work. It is not recommended to choose this diet to address weight, diabetes, or any chronic disease, nor to impact your long-term health.

Popular Diet #2: Keto Diet
What is it?
Keto diets, short for ketogenic diets, are predominantly fat – over 75% of calories come from fat, and most of the remainder comes from protein. The keto diet is a very lowcarbohydrate diet. The aim of the diet is to trigger a body process called ketosis, wherein you burn fat as fuel. Keto diets have been used for years to address epilepsy and similar serious neurological conditions.

What does the science say?
There is some science that suggests that people who follow this diet lose weight more quickly than they do by following a more moderate diet. The weight-loss advantage, however, seems to dissipate over time. A keto diet has been shown to improve blood sugar control for people with type-2 diabetes, at least in the short term. Some studies have suggested a risk of increased cholesterol. Unfortunately, there is inadequate data to know if this pattern can be part of a healthy eating plan over the long-term. This diet is heavy on notoriously unhealthy foods, such as red meat and other fatty, processed and salty foods.

Pros: Who might benefit & how might you benefit?
If you are someone with type 2 diabetes related to your weight, who enjoys a high-fat diet (avocados, meats, butter, nuts) this may work for you, with caveats. If you try this diet, closely monitor your blood sugar, but also your cholesterol, blood pressure and cardiovascular health, and drink plenty of water. This diet is best done under the guidance of a Registered Dietitian.

Cons: What to be aware of
• This is another nutritionally high-risk diet, this time due to its limitation on carbohydrate. Fruit is eliminated which increases risk of fiber and nutrient shortfalls.
• Hydration can become an issue and the demands on the kidneys is great - drink plenty of water.
• Don’t skip the vegetables, as they are the only source of fiber you’ll get.
• This diet is difficult to follow because of the great number of foods you cannot eat. It can be socially isolating.
• The long-term effects of the diet are not known.
• Not recommended if you are pregnant or have kidney issues. If you have health issues, you need to be monitored very closely.

The Bottom Line: Keto works for some but is a high-risk diet. For most people, there are better options available.