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It seems as though any time you turn on the TV or open up your social media feed there’s some diet approach that’s trending. And as usual, it promises lightning-fast results and better health.

As nutrition professionals, we get the confusion about diets. Most of these trends have a grain of truth and science to back them up, but the headlines seem to omit the individual nuance and potential pitfalls.

Although each one may tout that it’s the “best” option, we’d beg to differ. We are all unique individuals that require a more personalized approach to nutrition — at every stage of our lives.

So take a read and decide for yourself. Maybe one fits you like a glove, or perhaps you’ll find you prefer more of an à la carte option with the eating styles mentioned below. And still more, know that even if one approach suits you well today, your metabolism is dynamic and ever changing. Your approach often needs to evolve along with your age, health status, body composition, and activity level.

1. Intermittent Fasting

The Basics

Fasting isn’t new. It’s been around for thousands of years, and there is growing evidence for specific health benefits such as controlling inflammation, increasing lifespan, and supporting body-weight regulation. There’s also not only one way to do it. Some will fast for 24 hours one or two times a week. Others will eat low amounts of calories every other day to mimic some of the metabolic effects of fasting. The most popular approach lately, however, has been “time restricted eating,” which means you’re fasting for 12 to 20 hours, then “feeding” during the other 4 to 12 hours.

The Benefits

For clients who fast for 12 hours between bedtime and their first meal of the day (which lands them around lunchtime), it’s a simple way to help them manage their weight and calorie intake. They commonly report improved energy, and frequently have fewer gut issues when complying with this protocol.

Who it May Work For

It’s best for people who are already managing their blood sugar well (and note: one in three of us are not). It tends to also work well for people who can work out later in the day if it’s after their eating window. However, for those who are able to work out in a fasted state with adequate energy and without getting dizzy, this plan can work for the morning exerciser too.

Who it May Not Work For

If you normally wake up tired or starving, it’s probably not a good option for you, at least not right away. For athletes training multiple times per day, or for those doing high-intensity workouts in the morning, fasting may negatively affect performance and progress.

Also, men and women who are already lean (<8 percent body fat for men, <18 percent for women) may not see much body composition benefit from incorporating fasting, and they may face some challenges with maintaining lean mass if they do fast.


Pay attention to how you feel and drink plenty of water to stay hydrated (black coffee or tea are fine during fasting, too). Also, make sure you’re eating properly for your workouts and plan them around your fasting time.

Read more here: “Intermittent Fasting and Breakfast: The Ultimate Guide.”

2. Vegan

The Basics

Essentially, following a vegan diet means that you abstain from animal products and by-products, including honey and gelatin. Often, strict vegan will also give up using other products, such as clothing, made from animals as well. Years ago, its popularity was more often because of a religious belief or to support animal rights. While those reasons are still common, recently, this diet has become popularized after the release of a couple of buzzworthy documentaries. Today, it seems that people are interested in this eating style because of environmental concerns and worry over an unhealthy meat supply.

The Benefits

What’s great about this style of eating is (if you do it right) it automatically increases your plant and fiber intake. It has also been shown to reduce the risk for heart disease. It appears that plant-based eating is going to be an ongoing lifestyle trend because people are rightfully interested in quality foods and eating from the earth.

Who it May Work For

It’s best for someone who is knowledgeable about nutrition and how to properly balance macros, amino acid pools, and the intake of certain nutrients of concern with plant-based eating (such as iron, vitamin B12, creatine, carnitine, etc.). Or if someone lacks that knowledge, they are willing to hire a nutrition professional to learn more. It’s also best for someone open to using protein powders and nutritional supplements to help fill in any gaps. When done correctly and with precision, it can also be beneficial for an individual who wants to get their cholesterol and blood lipids in check.

Who it May Not Work For

I’ve had a lot of clients go through this style of eating and not stick to it because they feel weak or their blood-sugar regulation became a challenge. A lot of that may have to do with not getting the right balance of macros, especially protein. A subset of clients tend to feel fantastic initially, but after some time (think six to 12 months or more), they begin to struggle with significant hormone imbalances.

It can be a difficult approach to follow for those who are experiencing digestive issues, since it tends to be high in certain tough-to-digest carbohydrates (such as FODMAPS). Lastly, it’s not ideal for those who enjoy eating meat and want to simply replace it with meat-like vegan substitutes, as these are often highly processed, lack nutrient density, and result in a substantial carbon footprint.

If you feel like you are looking for a simpler approach or if you’re not feeling your greatest while sticking with an exclusively plant-based way of eating, this may not be the best plan for you.

Also, because most plant-based protein sources are dense in either carbohydrates (such as beans) or fat (such as nuts and seeds), it takes strategy (often with the use of protein powder) to stay lean. It’s not always a great option for people who want to lose weight.


I’d suggest your fat content be about 40 to 50 percent. Protein, at least 20 percent (more if you can swing it), and 40 percent carbohydrates. If weight loss is important to you, you can try to up the fat to 50 percent and add a rice- and pea-based protein powder several times per day.

The hardest nutrients to get with this diet are heme iron, vitamin B12, carnitine, and creatine — which are all found in animal products — so supplementing is a good option. Because of the high content of phytic acid in a vegan diet, which can hinder digestion of certain vitamins and minerals, you may also want to supplement with calcium and zinc. Sprouting your grains and beans can also help reduce phytic acid loads and help with absorption.

Aim to get a wide variety of protein in such as soy, nuts, and legumes. If you are choosing soy, make sure it’s non-GMO and organic. And because soy mimics estrogen in your body and can impact both men and women, you may want to consider confirming through blood work that you are clearing hormones.

Remember, it’s not uncommon to feel amazing at first, and then notice your body needs something different over time. Be sure to monitor how you’re feeling and functioning each month and year to verify it’s working for you.

3. Keto

The Basics

This protocol consists of eating a diet high in fat (70 to 80 percent), low in carbs (<10 percent) and moderate in protein (10 to 20 percent). It’s high enough in fat and low enough in carbohydrates to achieve measurable levels of ketones in the blood to create ketosis, which reduces feelings of hunger. The idea behind this diet is that you’ll start burning fat instead of glucose for energy.

In clinical dietetics, a ketogenic diet is often used in children with epilepsy as a way to control seizures. Recent studies have shown the positive impact the right fats can have on your brain (and also what the potential negative effects of sugars and processed foods are).

The Benefits

For some, the high-fat content of this diet can keep people feeling full (so they’ll eat fewer calories) and drive fat loss. Burning fat (versus glucose) for energy in theory can also lead to more significant fat loss. Since the diet is low in carbohydrates and added sugars and refined grains are removed, that can show a massive health and function benefit. And it has shown in some research to help people to lose weight more sustainably than a lower fat, calorie-restricted diet — possibly because of a smaller decrease in resting metabolism. Additionally, those in ketosis often report clearer thinking and cognition.

Who it May Work For

It’s been exciting to watch how this has emerged from a specialized diet treating pediatric seizures into a popular approach for adults, and it can potentially help whether someone is looking to lean out or control health conditions. It has also been shown to help people who struggle with depression or certain hormonal issues. Notably, it may be of benefit to individuals with metabolic syndrome, insulin resistance, and diabetes.

Also interesting to note: In studies where individuals who are obese combined a ketogenic diet with resistance training, there was a significantly greater fat loss compared to a group who ate a “standard” healthy diet and performed the same training program. The results are so compelling that the Swedish Medical Board now recommends the ketogenic diet as a first-line therapy for obesity treatment.

Who it May Not Work For

I’ve had clients who love this eating style and then those who experienced the exact opposite of the intended results. Some noticed an increase in gut issues, including the inability to digest and absorb the amount of dietary fat required, especially in those who have gallbladder issues. It also might not be best for those with certain thyroid conditions, chronically high cortisol, or an intense exercise training program.

Keto is not for everybody, and you don’t want to stay on it if you don’t feel well. The more that research uncovers about genetics and metabolism, the more we will learn about why certain eating styles only work for certain people.

For most, a ketogenic approach is best when it’s short-term (think two to six weeks). When a diet is extreme in what is cut out, like carbs, it can feel too restrictive and can limit social interactions. Studies have also suggested that for those who are overweight and insulin sensitive (versus insulin resistant or pre-diabetic), the ketogenic approach is less helpful for fat loss.


Drink plenty of water to keep hydrated; this will decrease the effects of the shifts happening internally. Because you are not getting many carbs, which hold onto water, you will be more apt to become dehydrated, so consider adding in extra electrolytes too.

Evidence also suggests following a resistance-training program when on a ketogenic diet. Without the addition of resistance training, you risk losing significant amounts of skeletal muscle. Because of the extremely low calories coming from carbohydrates, those sticking to this diet need to limit their intake of full-fat dairy, starchy veggies, legumes, and nuts. It’s also important to avoid any type of sugar, processed foods, grains, and sweetened beverages.

Lastly, if you’re going to try the ketogenic approach, be sure that you’re on-board with consuming plenty of fibrous and non-starchy vegetables as your primary source of carbohydrate. Think along the lines of asparagus, dark, leafy greens, and cruciferous vegetables such as broccoli and cauliflower.

Read more here: “Keto: Health Benefits, Cautions, and Controversies.”

4. Paleo

The Basics

Some clients love this diet because its concepts are simple: basically, you’re going back to nature and primarily eating produce, nuts and seeds, and high-quality proteins like eggs, fish, poultry, and meat. It emphasizes quality foods, such as making sure beef is grass-fed and poultry is pastured. Things that are cut out while on this diet include dairy, grains, beans, legumes, peanuts (since they are a legume), processed foods, and sugars (although honey is approved in moderation).

The Benefits

A good chunk of us (some estimates say two-thirds) do have problems with dairy, so taking it out may be helpful for a decent percentage of people. Gluten can also cause issues for many individuals, and our high intake of grains and processed foods can interfere with achieving an optimal body composition because they’re so easy to overeat. For many, this diet can help to keep an individual’s weight in check. It generally encourages the intake of unprocessed, high-quality food.

Who it May Work For

The paleo approach has increased in popularity over the past decade. When it’s well-balanced with produce, healthy fat, and protein, it’s a great option for many people because it’s fairly easy to follow and most people do well on it. This proportional balance can support maintenance of healthy blood-sugar regulation and control, and therefore help with body composition and management of cravings.

Who it May Not Work For

There are some people who do not experience any negative effects from dairy and gluten consumption. (The only way to truly know is with an elimination diet and reintroduction trial.). So if you like to eat dairy, grains, and legumes and don’t see forgoing them as an option — or if you limit your animal protein intake — this may not be the right diet for you.

If you are an athlete or have a macro plan that requires higher amounts of carbohydrates, extra planning might be needed to get in the right amounts of root vegetables to meet your needs since grains are excluded on strict paleo.


While we can always learn about our ancestor’s diet approaches, many gurus promoting this lifestyle can breed an unrealistic “all or nothing” attitude about food which can be a little rigid and restrictive. If you want to follow this way of eating but still want to consume a little dairy or legumes, don’t be hard on yourself about it.

What Might Be Best For You?

Everything boils down to individualization — and the importance of finding what works for you at this point in time. Try not to hone in too much about what your neighbor, best friend, or trainer is eating. Pay attention to your body and what makes it feel most optimal. And know that what works for you now may be different than what works for you in six to 12 months.

It may help to start with a clean-eating detox to get a fresh start, focus on nutritious foods in a reasonable balance, and do a structured reintroduction of certain foods so that you can learn about what helps your body thrive (or not).

If you want to take it to the next level, arm yourself with fully individualized information about your unique metabolism through an annual comprehensive blood test. Ideally, assess food sensitivities, nutrition status, blood-sugar regulation, cholesterol, cortisol, inflammation, and hormone balance.

Your best-case scenario is to assess your personal physiology, then develop a nutrition approach that is more likely suited to your needs.  Our most successful clients usually start with comprehensive lab testing before embarking on weight loss or fitness gain efforts, and they reassess any areas of concern every three to six months or so.

Be leery of gurus or practitioners that only recommend and identify with one specific eating strategy or diet. While they might get amazing results (which is awesome), they might be blinded by their personal experience and forget that it might not work for everyone.

There really is no one-size-fits-all approach. Our team of dietitians at Life Time has been slightly ahead of the curve as far as the pros and cons of what’s “trendy” because we have amazing access to our own lab testing to better understand current physiology, and we love staying on top of current research to help best support those pursuing their goals.

Start the journey with a goal of figuring out what is right for you. 

Keep the conversation going.

Leave a comment, ask a question, or see what others are talking about in the Life Time Health Facebook group.

Samantha McKinney, RD, CPT

Samantha McKinney has been a dietitian, trainer and coach for over 10 years. At first, her interests and experience were in a highly clinical setting in the medical field, which ended up laying a strong foundation for understanding metabolism as her true passion evolved: wellness and prevention. She hasn’t looked back since and has had the honor of supporting Life Time’s members and nutrition programs in various roles since 2011.

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