Flexible Dieting verses Keto Diet

Flexible Dieting verses Keto Diet

Master of Dietetics, Bch Food Science & Nutrition
Online Physique Coach

What is Flexible Dieting?

Flexible dieting is a relatively new nutrition concept, which focuses on tracking the macronutrient composition of foods in order to achieve one’s desired body shape. What differentiates flexible dieting from other diet strategies is that it does not restrict food groups, but rather permits the consumption of all foods so long as the food product chosen adheres to the individual’s set macronutrient targets. The diet is typically moderate in protein, with around 2.5g of protein per kilogram of lean muscle, with moderate amounts of fat and carbohydrates which make up the remaining calories in order to achieve their desired body composition. However, a flexible dieting approach can theoretically be used with any kind of macronutrient breakdown so long as those macronutrients are accounted for in the individual’s daily totals. In this way flexible dieting is not a ‘diet’ per say, but rather a system of dieting.

The concept was originally gained popularity with bodybuilders who were becoming tired of inflexible and restrictive dietary practices during contest preparation.
Rather than adhering to a rigid meal plan, bodybuilders would track their daily protein, carbohydrate, and fat intake, which enabled them to enjoy a wider variety of foods and better conform to their daily nutritional requirements.

Have your cake and eat it too!

The premise of flexible dieting is that the body does not differentiate between individual foods. There are no ‘good’ or ‘bad’ foods, but rather what is important is the macronutrient composition of each food. For example carbohydrates from whole wheat pasta would be equivalent to a pop tart if they provided they same amount of carbohydrate as they would both breakdown into their constituent sugars in the body. Provided the carbohydrate, fat and protein content of the food selected fits within the individuals daily macro targets, food choices are at complete at the discretion and preference of the individual, as opposed to adhering to a strict meal plan.

What else does the diet require?

Flexible dieters are also required to track their fibre intake, as this encourages the consumption of wholesome, fresh, plant based foods, which not only assists in meeting daily fiber requirements, but also promotes thermogenesis and digestive health. Consuming enough fiber also increases the likeliness of flexible dieters adhering to the individuals set nutrient reference values for all essential micronutrients.

As a general rule, flexible dieters should first look to meet their overall caloric and macronutrient needs by including a wide variety of ‘nutrient dense’ foods. This can be achieved by consuming plenty of fresh fruits and vegetables, breads, grains and cereals, dairy and dairy alternatives, nuts & seeds, as well as lean red meats, poultry, seafood, eggs and various other protein sources.

For vegetarians following flexible dieting, it is important to first include the highest quality plant based proteins, specifically soy-derived products such as tempeh and tofu, since their amino acid profiles offer a superior / profound effect on muscle protein synthesis than compared to other plant based protein sources.

Only once these basic needs are met, should flexible dieters consume calories from more processed take away foods.

The key to flexible dieting

To begin flexible dieting, an individual must first determine their total daily caloric intake, along with accurate macronutrient ratios, which are specific to their desired physique or sporting goal. Caloric intake and macronutrient ratios can be calculated by a health professional such as Dietitian or Nutritionist or other suitably qualified nutrition expert.
Websites such as IIFYM.com have macronutrient calculators that can provide a great starting point for determining your macronutrient breakdown based on your goals. My website also offers a variety of flexible dieting programs. These are specific to your physique or sporting goal, and can also provide you with a semi-custom diet plan to help you get started with flexible dieting as you begin to learn how to track your macronutrients.

The pro’s and con’s of flexible dieting

Unlike other fat loss dietary strategies, flexible dieting does not prohibit the consumption of specific food groups or food types, including take away foods, therefore the temptation to consume more of these junk style food types is often greater. For a variety of reasons, processed, take away foods are more energy dense than an equivalent home cooked version. Food manufactures and restaurant owners want their products to taste good to encourage repeat purchase, and the addition of fats and sugars are often necessary to increase the shelf life of packaged goods. Thus, flexible dieting with the inclusion of more processed foods, typically limits the total volume of food able to be consumed in a day, which could possibly lead to feelings of increased hunger, thus making the diet more difficult to adhere to. However this is usually a concern for those in a calorie restricted state and can be avoided with careful planning.

Abusing the freedom

Many people misinterpret flexible dieting as a license to consume as much processed junk food as they like. While the basic concept of flexible dieting is rather straightforward, many people will misinterpret the information and the importance of vitamins and minerals and their various functions within the body are overlooked, including the production of hormones, energy metabolism, digestion, immune function and overall health. Having a knowledgeable nutrition coach or educational resource can help flexible dieters better adhere to their micronutrient requirements.

Tracking foods & eating out

For someone new to flexible dieting, familiarising themselves with the weight of food and counting macronutrients intakes can be time consuming and overwhelming. However there are a range of books, mobile phone apps and online resources that can simplify the tracking process for flexible dieters. Easy Diet Diary is a great mobile app for Australian consumers and My Fitness Pal, which contains over 5 million food products world wide.

While flexible dieting allows greater food diversity, it can be challenging to find restaurants that provide their foods macronutrient information. For restaurants that do not display nutritional information, it becomes very difficult for the inexperienced flexible dieter to know exactly what they are consuming and how to track mixed meals. We could argue however, that even if the nutrition information is listed, it is not a guarantee, as the chef’s main concern is ensuring the food being served is safe and tastes good and unlikely to be weighing out exact measurements of ingredients. Similarly said, we could also argue the accuracy of daily energy intakes for any dieting strategy, as macronutrients listed on packaged food products have a 20% variance, so knowing the nutritional value of a food doesn’t necessarily ensure 100% accuracy. If a restaurant does not list the macronutrient composition of their meals there are two simple ways to estimate your intake. 1) Input each individual ingredient in the food along with the amount you believe was in the dish. While tedious, this can work quite well for the seasoned flexible dieter. 2) Search food databases for other similar dishes and take the average of the macronutrient breakdowns you find.

The key positive to flexible dieting is that it encourages food variety and allows for the inclusion of foods you enjoy and flavours your love. This is important because it means you are far more likely to adhere to the dietary protocols in a calorie restricted state, and research shows that the most successful long-term dieting strategies are those that permit adherence and are sustainable in the long term.


Part 2. Ketogenic Diets

How is flexible dieting different to a ketogenic diet?

While many people view flexible diets and ketogenic diets as mutually exclusive, that isn’t necessarily the case. While it is true that most flexible diets allow for a moderate or even high carbohydrate intake, and ketogenic diets are very low in carbohydrate, one could still follow a ketogenic style diet while flexible dieting, by tracking their macronutrients, just ensuring that they consume a low carbohydrate/high fat macronutrient breakdown. The main difference between traditional flexible diets and ketogenic diets is that a ketogenic diet is a very high fat diet, moderate to low in protein and very low in carbohydrate, which causes a shift in primary metabolic fuel source from carbohydrates to fats. It also alters fat metabolism so the body produces compounds known as ketone bodies in the liver. These compounds include such as aceto-acetate & beta-hydroxy-buterate. These ketones can be used as energy in tissue like skeletal muscle and more importantly, brain. Under normal conditions, the brain exclusively uses glucose for energy, but in a ketogenic state, the brain will shift to using ketones as a fuel source in order to spare blood glucose for essential tasks such as red blood cell metabolism (red blood cells can only use glucose as fuel since they lack mitochondria). Keep in mind that even with zero carbohydrate intakes, the liver can produce about 120g of glucose per day in a process called gluconeogenesis (GNG) for essential tasks from substrates like amino acids and other gluconeogenic metabolites.

Why are carbohydrates viewed as the bad guys?

Dietary strategies such as flexible dieting that include the consumption of carbohydrates, are often viewed as less than optimal for achieving a desirable body composition, due to the fact that they can lead to insulin resistance through increased insulin secretion. Insulin is a hormone that is released when blood glucose rises and shuttles glucose into various tissues including muscle and fat. Due to this, insulin is frequently referred to as a storage hormone and thus many people have made recommendations to avoid carbohydrates at all costs.

Carbohydrates and Insulin: Are they the primary cause of bodyfat gain?

Since carbohydrates do increase insulin, and insulin is a storage hormone, many people have made large leaps of logic to point the finger at carbohydrates as being the primary cause of fat gain and obesity as opposed to overall caloric intake. They also point out that in a ketogenic diet, carbohydrates are not being used as fuel, whereas fats become the primary fuel. Their logic is, eat more fat, burn more fat. While that is true to a certain extent, it’s not quite that simple. These individuals miss the fact that by limiting carbohydrate to very low levels in the diet, you are typically going to restrict calories as well. In fact, many people have become so passionate about low-carb lifestyles that they become keto-zealots, rather than considering the science of what actually makes a fat loss diet successful. This debate is a major factor why ketogenic diets are such a hot topic right now, but are they inherently superior for fat loss when compared to flexible dieting?

Ketogenic diets are not superior to flexible dieting.

There are several studies that keto-zealots often point to in order to support claims of a ketogenic diet being superior for loss over diet strategies such as flexible dieting.

For example, a recent meta analysis published in 2013, compared very low calorie ketogenic diets (VLCKD) to low fat diets with a minimum of 12 months of follow up. They found that individuals who were assigned to the VLCKD, were able to achieve greater weight loss than participants in the low fat groups. What this study does not consider is that the research studies selected for inclusion in this analysis did not equate for protein and in some cases even overall calorie intake. So it’s likely that greater weight loss was achieved in VLCKD by default, since we know ketogenic diets can be more satiating and often people will consume lower calories than in low fat, high carbohydrate diets, such as protocols employed by flexible dieting. These studies also did not control for protein, which is often higher in a ketogenic diet vs. a low fat, high carbohydrate diet.

So what does the science say? When calories and protein are equal, a ketogenic diet does NOT seem to offer any additional fat loss benefit compared to an equal calorie, equal protein non-ketogenic diet according to a study published in 2006 in the American Journal of Clinical Nutrition from Arizona State University. In this highly controlled study, both groups lost an almost identical amount of weight and bodyfat. This tells us that for fat loss, you could use either flexible dieting or a ketogenic diet. I suggest following the diet strategy your best able to stick to long term.

Pro’s and con’s of ketogenic diets

The major mistake I see for people using a ketogenic diet is they do not adhere to the correct ratios of macro-nutrients necessary to ensure ketone production. For example, adherence to low carbohydrate is usually met by most, however the ratio of protein to fat is often too high. On a traditional ketogenic diet, carbohydrate intake is usually about 5-10% of total caloric intake, protein is 10-15%, and fats are around 80%. Currently, the most popular form of keto is a modified ketogenic diet which puts carbohydrate intake around 5-10% of total caloric intake, protein at no more than 20-25% of total energy intake and fats should make up the majority of total calories at approximately 70% of calories.
In a carbohydrate-restricted state, the body calls upon its secondary energy sources, namely fats and proteins in order to function. Here, protein is converted to glucose through the process known as gluconeogenesis in the liver as described previously. This is why it is important to ensure your protein is not providing greater than 20-25% of your total caloric intake while following a ketogenic diet, as too much protein results in glucose production and remains the primary energy source, as opposed to fats or ketone bodies.

Abusing the freedom

The idea of being able to eat plenty of high fat foods at every meal may sound highly appealing to some, but doesn’t come without nutritional consequences. Eliminating carbohydrates, like any diet that restricts whole food groups, makes it far more difficult to meet daily micro-nutrient requirements, in particular B- vitamins. It is important to make sure you consume a wide variety or fresh vegetables, as these are essential for their rich source of fibre, vitamins and minerals, antioxidants and other important micronutrients.

In any case, I strongly recommend taking a multi-vitamin as well as an iron supplement, especially for those adhering to low caloric intakes, since it is difficult to consume a sufficient iron, and reasonable to ask without essentially all protein sources being provided by lean red meat.

Health benefits of ketogenic diets

There is data to support a benefit of a ketogenic diet in a number of medical conditions such as epilepsy, Alzheimer’s, cancer, and type 2 diabetes. In these conditions, providing an alternative fuel source instead of carbohydrate seems to have a therapeutic effect. In the case of type 2 diabetes, using ketones as fuel instead of glucose can help lower blood glucose levels. It is important to point out however, that type 2 diabetes also improves during any form of caloric restriction, and it is likely that a ketogenic diet is not unique in that aspect, rather it is causing a caloric deficit by severely restricting carbohydrate intake. This being said, flexible dieting could arguable yield a similar outcome in a caloric deficit.

Ketogenic diets have been found to be helpful for a number of types of cancers, specifically glucose obligate cancer types, meaning they can only grow with glucose present, as the tumours use it as exclusive fuel. Thus by limiting carbohydrate intake and forcing our bodies to use fats and ketone bodies instead of carbohydrate, can have a therapeutic effect by essentially ‘starving’ these tumors. Please keep in mind this is not a ‘cure’ for cancer and some cancers are not glucose obligate users. If you have cancer you should ALWAYS follow your oncologists recommendations for your specific disease.

Some studies have reported less feelings of hunger when following a ketogenic diet, and this is believed to be linked to fats being more satiating resulting from slower digestion and extended feelings fullness. However flexible dieters could also argue that they feel more satiated with the inclusion and wide variety of foods groups.


Any nutrition plan that sees you in a caloric deficit is going to result in fat loss. If you prefer high fat foods in preference to carbohydrate containing foods, particularly during a phase of calorie deficit and you find it easier to adhere to, then by all means try a ketogenic diet. If you equally enjoy eating carbohydrate containing foods and prefer the inclusion of a wide variety of food products, then flexible dieting may be better for you. There is little benefit to following a diet strategy that is not maintainable long term. Many people will lose weight only to pile the pounds back on after regular foods are reintroduced. There are a wide variety of dietary approaches that can all be equally effective for improving body composition when calories and protein are equated, so when it comes to overall body composition and fat loss, choose an approach that is sustainable for you.

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