Dietary restriction: definitive guide

Dietary restriction and calorie restriction are related but distinct concepts.

The dietary restriction generally refers to any intentional modification of food intake for the purpose of promoting health, managing medical conditions, or improving weight management. This can involve changing the types of foods consumed, such as reducing the intake of high-fat or high-sugar foods or altering the timing or frequency of meals. For example, a person may choose to follow a low-carbohydrate diet, a plant-based diet, or an intermittent fasting regimen to achieve specific health or weight goals.

What is the difference between caloric restriction and dietary restriction?

Dietary restriction is about the content of food, whilst calorie restriction, on the other hand, specifically involves reducing calorie intake below the usual levels consumed in order to promote health, extend lifespan, or improve weight management. Calorie restriction can be achieved through various methods, such as reducing portion sizes, limiting the intake of high-calorie foods, or using fasting techniques.

While dietary restriction and calorie restriction can overlap, they are not necessarily synonymous. A person may follow a specific dietary pattern without reducing overall calorie intake, or they may reduce calorie intake without making significant changes to the types of foods consumed. It is important to note that any dietary or calorie modifications should be made in consultation with a healthcare professional or registered dietitian to ensure that they are safe and effective for individual needs and health status.

Are there health benefits to dietary restriction?

Animal and human studies

Studies in animals have shown that both DR and CR can lead to increased lifespan and improved health outcomes, such as a reduced risk of chronic diseases.

There are very few studies that look deeply into what dietary restriction is for humans. Part of the reason for the lack of studies is that humans live long lives, comparatively. Maintaining dietary restrictions requires conscious effort and discipline. Monitoring dietary restrictions over years is expensive in human studies. However, there is some research on the ways we can measure health and estimate lifespan.

There have been several studies conducted on rodents, primates, and humans to investigate the effects of dietary restriction on health, longevity, and disease risk. Here are some findings from studies of dietary restriction and the Standard American Diet:

1. Rodents: Studies of dietary restriction in rodents have consistently shown that reducing calorie intake and limiting consumption of calorie-dense, nutrient-scarce foods can improve health and extend lifespan. For example, a study published in the journal Nature Communications in 2020 found that a low-calorie diet improved metabolic health and reduced age-related decline in mice, even when the diet was initiated in middle age (Mitchell et al., 2020).
2. Primates: Studies of dietary restriction in primates have also shown promising results for health and longevity. For example, a study published in the journal Nature in 2009 found that rhesus monkeys fed a calorie-restricted diet had lower rates of age-related diseases, such as cancer and diabetes, and lived longer than monkeys fed a normal diet (Mattison et al., 2009).
3. Humans: While there have been fewer studies on dietary restriction in humans, there is evidence to suggest that reducing the consumption of calorie-dense, nutrient-scarce foods can improve health and reduce disease risk. For example, a study published in the Journal of the American College of Cardiology in 2017 found that a diet that emphasized whole, nutrient-dense foods and limited consumption of processed foods and sugary drinks improved cardiovascular health in overweight and obese adults (de Souza et al., 2017).

The evidence suggests that reducing the consumption of calorie-dense, nutrient-scarce foods, such as processed and junk foods, can have significant health benefits for both animals and humans. However, it is important to note that the specific dietary approach that is most effective may vary depending on individual needs and preferences and should be made in consultation with a healthcare professional or registered dietitian.

What to include in the diet and what to exclude?

The question is what to include in the diet and what to exclude.

Opinions on that vary and besides medical considerations such as allergy-specific diets and diets aimed to alleviate symptoms of various conditions such as diabetes, there are also ethical considerations (vegetarianism, veganism, etc), religious considerations (halal, kosher, etc ) and economic considerations as everyone is on a different budget.

Most common dietary restrictions for losing weight, improving health, and living longer

There are many different types of dietary restrictions that people may try to lose weight, improve health, and live longer. Some of the most common dietary approaches for weight loss, improved health, and longevity include:

1. Low-carbohydrate diets: These diets limit the consumption of carbohydrates, such as bread, pasta, and sugary foods, and emphasize foods that are high in protein and healthy fats, such as meat, fish, eggs, nuts, and seeds.
2. Mediterranean diets: These diets emphasize the consumption of whole, nutrient-dense foods, such as fruits, vegetables, whole grains, fish, and healthy fats like olive oil, and limit the consumption of processed foods and red meat.
3. High protein diets: These diets are common among athletes who need protein to build and maintain muscle.
4. Intermittent fasting: This involves alternating periods of calorie restriction with periods of normal or increased calorie intake, such as alternate-day fasting or periodic prolonged fasting.
5. Time-restricted eating: This involves limiting the daily eating window to a certain number of hours, such as 8 hours or less while maintaining normal calorie intake.

It is important to note that the most effective dietary approach for weight loss, improved health, and longevity may vary depending on individual needs and preferences, as well as medical history and other health factors. It is recommended to consult with a healthcare professional or registered dietitian before making any significant dietary changes.

Allergy and medical condition diets

There are several types of dietary restrictions based on medical conditions or allergies. Some examples include:

• Gluten-free diets for those with celiac disease or gluten intolerance, gluten is a general term for the proteins found in wheat, rye, barley, and triticale – a cross between wheat and rye. It helps foods maintain their shape and acts as a glue of sorts. Research suggests that about 6% of the U.S. population is gluten intolerant. It’s more common than more severe but similar celiac disease, which affects about 1% of the population.
• Dairy-free diets for those with lactose intolerance or milk allergies. Milk and milk products such as cheese contain lactose. While most infants can digest lactose, many people begin to develop lactose malabsorption—a reduced ability to digest lactose—after infancy. Experts estimate that about 68 percent of the world’s population has lactose malabsorption. Lactose intolerance is more severe and less common.
• Low-FODMAP. FODMAP is a diverse group of carbohydrates whose presence in the diet is thought to contribute to the symptoms of irritable bowel syndrome (IBS). According to research, approximately 15 percent of the population is intolerant to FODMAPS, in the United States, this figure is likely to be similar in other Western world countries.
• Low-salt diets for those with high blood pressure. Spicy foods and sauces in particular are rich in salt.
• Low-purine diets for those with gout. Purines are chemical compounds that form uric acid when metabolized. Alcohol, some meats, and some fish are purine-rich.
• Low-histamine diets for those with histamine intolerance. Histamine-rich foods are alcohol, fermented products, and some fruit and vegetables.
• Low-carb diets for those with diabetes.
• Low-fat diets for those with high cholesterol.
• Low-protein diets for those with kidney disease.

It’s important to note that these dietary restrictions should be followed under the guidance of a registered dietitian or physician, as they may not be suitable for everyone and may lead to nutrient deficiencies if not properly planned.

Diet philosophies

• Ethical/philosophical/plain preference dietary restrictions (that can combine with health considerations):
  • Vegetarianism is a dietary practice that avoids the consumption of meat and fish but may include dairy and eggs;
  • Veganism is a dietary practice that avoids all animal products;
  • Pescatarianism is a dietary practice that avoids meat but includes fish; other ethics-based dietary restriction practices include
  • Flexitarianism, which is a plant-based diet with occasional meat consumption, and
  • Pollotarianism, which avoids red meat but includes poultry.
  • Carnivore diet excludes vegetables, fruit, and greens and only includes, animal products such as meat, poultry, eggs, milk, cheese, and fish.

Some ethical philosophies of dietary restrictions are aimed at reducing harm towards other living beings, some are deeply rooted in religion, and others are strictly on a secular mindset. The carnivore diet, which is very niche, is mostly based on health considerations alone. It’s important to note that individuals within each dietary-preference group will have their own personal dietary choices and restriction, it’s not necessary to be strictly followed by all of that particular group.

Religious dietary restrictions

• Religious dietary restrictions:
  • Judaism / Kosher: In Judaism, there are laws of kosher that govern what foods are permissible to eat and how they must be prepared. Pork and shellfish are not permitted, and meat and dairy must be kept separate.
  • Muslim/ Halal: In Islam, there are laws of halal that govern what foods are permissible to eat. Pork and alcohol are not permitted, and animals must be slaughtered in a specific way.
  • In Hinduism, there are dietary restrictions based on caste and personal beliefs. Some Hindus do not eat meat, while others do not eat beef.
  • In Buddhism, there are no specific dietary restrictions, but many followers choose to follow a vegetarian diet as a way to reduce harm to animals.
  • In Jainism, there are strict guidelines for food consumption, with many followers following a vegetarian diet and avoiding root vegetables to reduce harm to microorganisms.
  • In Christianity, there are no specific dietary restrictions, but some branches advocate for a vegetarian or vegan diet as a way to promote peace and respect for life.

Religious dietary restrictions can vary from region to region and the availability of foods.

It’s important to note that individuals within each religion may have their own personal dietary choices and restriction, it’s not necessary to be strictly followed by all members of a religion.

Health benefits of cutting down on processed high-carb foods

Cutting down on high-carb processed foods can have several health benefits, including:

1. Improved blood sugar control: Consuming high-carb processed foods can lead to rapid spikes in blood sugar levels, which can increase the risk of insulin resistance, type 2 diabetes, and other metabolic disorders. By reducing the intake of these foods, blood sugar levels can be better controlled.
2. Reduced inflammation: High-carb processed foods can also promote inflammation in the body, which is linked to a range of chronic health conditions, including heart disease, cancer, and autoimmune disorders.
3. Weight loss: High-carb processed foods are often high in calories and low in nutrients, which can contribute to weight gain and obesity. By reducing the intake of these foods, weight loss can be achieved.

The evolutionary response that makes us consume more calorie-dense foods that we do not need is known as the “thrifty gene hypothesis”. This hypothesis suggests that our ancestors evolved to be more efficient at storing calories during times of plenty, in order to prepare for periods of famine or food scarcity. However, in modern times, where food is readily available and often high in calories, this evolutionary response can lead to overconsumption and weight gain.

In addition to the thrifty gene hypothesis, there are also several environmental and psychological factors that can contribute to the overconsumption of high-calorie, nutrient-scarce foods, such as food marketing, stress, and emotional eating. By becoming more aware of these factors and making conscious choices to reduce our intake of processed and calorie-dense foods, we can improve our health and reduce the risk of chronic diseases.

References

References: de Souza RJ, Mente A, Maroleanu A, et al. Intake of saturated and trans unsaturated fatty acids and risk of all cause mortality, cardiovascular disease, and type 2 diabetes: systematic review and meta-analysis of observational studies. BMJ. 2015;351:h3978. doi:10.1136/bmj.h3978

Mattison JA, Roth GS, Beasley TM, et al. Impact of caloric restriction on health and survival in rhesus monkeys from the NIA study. Nature. 2009; 400:174-180.

Mitchell SJ, Bernier M, Mattison JA, et al. Daily fasting improves health and survival in male mice independent of diet composition and calories. Nat Commun. 2020;11(1):3704. doi: 10.1038/s41467-020-17483-2.