The quest for optimal health and well-being has led to the exploration of various dietary strategies. Among these, non-eating diets, particularly intermittent fasting and plant-based approaches, have garnered significant attention. While these diets promise potential benefits, it's essential to understand their mechanisms, weigh the risks, and consider individual suitability.
Intermittent Fasting: A Time-Restricted Eating Pattern
The obesity epidemic has spawned a cottage industry of weight-loss schemes. Currently in vogue is intermittent fasting, which involves alternating intervals of extreme calorie reduction with periods of normal eating. Intermittent fasting achieves weight loss by severely limiting calories during certain days of the week or during specified hours during the day. One pattern that has become a bit popular is the so-called 5:2 diet. With this system, you eat normally for five days of the week, but restrict food intake to just 500 to 600 calories on the two fasting days.
Potential Benefits of Intermittent Fasting
- Weight Loss: Intermittent fasting, like all diets, achieves weight loss through the same equation - you take in less food energy each day than your body burns for normal activity. Fasting 1 or 2 days a week may be a way to consume fewer calories over time, which may be easier than cutting back a certain number of calories every day.
- Metabolic Improvements: Regular intermittent fasting may help improve how your body breaks down cholesterol and sugar. These changes to your metabolism may help reduce your risk of developing conditions like diabetes and cardiovascular disease. The energy restriction from a 24-hour fast may also benefit your metabolism, helping in weight loss.
- Cardiovascular Health: A regular 24-hour fast may help reduce trimethylamine N-oxide levels in the long term. High levels of this compound are tied to coronary artery disease, so this may help reduce your risk. There have been some really intriguing studies suggesting that a pattern of intermittent fasting may improve your blood pressure, improve your cholesterol, and really lead to weight loss.
- Diet Psychology: Intermittent fasting may have a beneficial effect on diet psychology for some people. One of my patients felt strongly that he didn't want to be bothered with tracking calories and filling out food records. Instead, he opted for a 5:2 fasting approach, which has worked well for him so far.
- Cellular Mechanisms: Part of the fascination with intermittent fasting arises from research with animals showing that fasting may reduce cancer risk and slow aging. One hypothesis is that fasting can activate cellular mechanisms that help boost immune function and reduce inflammation associated with chronic disease.
Risks and Considerations of Intermittent Fasting
- High Dropout Rate: A notable aspect of a trial published July 1, 2017, in JAMA Internal Medicine, was a very high dropout rate (38%) among the people assigned to the fasting regimen. This may reflect a real-life pitfall of fasting as a weight-loss approach.
- Potential for Unhealthy Dietary Habits: It's human nature for people to want to reward themselves after doing very hard work, such as exercise or fasting for a long period of time, so there is a danger of indulging in unhealthy dietary habits on non-fasting days. In addition, there's a strong biological push to overeat following fasting periods.
- Not for Everyone: While intermittent fasting has promise, it’s not right for everyone. A lot of the research has been done in animals, so it’s not clear if people would get all of the same benefits. And early studies mostly looked at the more extreme 5:2 diet. Fasting might not be a good idea for certain groups or people with some health problems.
- Cardiovascular Risks: adults found that people who limited their eating across less than 8 hours per day were more likely to die from cardiovascular disease compared to people who ate across 12 to 16 hours per day.
- Side Effects: Frequently fasting for 24 hours at a time can lead to side effects and increase your risk for certain complications. Always talk with a doctor before going on a fast to help reduce your risk for any unforeseen health consequences. This is particularly important if you have underlying health conditions.
- Contraindications: Skipping meals and severely limiting calories can be dangerous for people with certain conditions, such as diabetes. People who take medications for blood pressure or heart disease also may be more prone to electrolyte abnormalities from fasting. You shouldn’t fast if you:have or have had an eating disorder, have type 1 diabetes, are pregnant or breastfeeding or chestfeeding, are under the age of 18, are recovering from surgery.
- "Hangry" Feelings: Although this technique may seem easier than cutting back on daily calories, you may find yourself quite “hangry” on fasting days. It can also cause severe side effects or complications in people with certain health conditions.
Important Considerations for Intermittent Fasting
- Consult a Doctor: If you are considering intermittent fasting, make sure to discuss it with your doctor.
- Sustainability: The main goal is to develop a healthy eating pattern that is sustainable and can support weight loss over time.
- Toxic Food Environment: We live in a toxic, obesogenic food environment.
- Hydration: During a 24-hour fast, it’s important to drink plenty of water-more than your usual 8 glasses. You won’t be ingesting any water from food during this time, and your body needs water to function. Water helps your digestive system regulate your body temperature benefits your joints and tissues, and can keep you feeling energized. You should drink water as you feel thirsty throughout the day. The amount you should drink varies from person to person and depends on your activity level.
- Preparation: You can perform a 24-hour fast whenever you choose. You just have to make sure that you prepare for your fasting day in advance. Eating healthy and well-rounded meals prior to the fast will help your body get through the 24-hour period. Foods high in fiber can help your body feel full long after eating. Fruits and vegetables contain water, giving you more hydration.
Plant-Based Diets: Harnessing the Power of Plants
Plant-based diets have become increasingly popular thanks to their purported health benefits and more recently for their positive environmental impact. There are different types of plant-based diets, but in this review, we will focus our attention primarily on vegan (100% plant-based), lacto-ovo vegetarian (i.e. plant-based except for dairy products and/or eggs), and pesco-vegetarian or pescatarian (i.e. plant-based except for fish and seafood with or without eggs and dairy) diets. All vegetarian diets exclude meat (e.g. According to the American and Canadian Dietetic Associations, appropriately planned and supplemented vegan and lacto-ovo vegetarian diets are nutritionally adequate and suitable for individuals in all stages of the life cycle and may provide health benefits in disease prevention and treatment.
Potential Benefits of Plant-Based Diets
- Reduced Risk of Chronic Diseases: Prospective studies suggest that consuming vegetarian diets is associated with a reduced risk of developing cardiovascular disease (CVD), diabetes, hypertension, dementia, and cancer. Data from randomized clinical trials have confirmed a protective effect of vegetarian diets for the prevention of diabetes and reductions in weight, blood pressure, glycosylated haemoglobin and low-density lipoprotein cholesterol, but to date, no data are available for cardiovascular event rates and cognitive impairment, and there are very limited data for cancer.
- Cardioprotective Mechanisms: Multiple nutritional effectors of a healthy vegetarian diet modulate important metabolic, hormonal, and immune factors associated with the development of cardio- and cerebrovascular diseases. Several factors can explain why vegetarians have significantly lower levels of plasma cholesterol, especially when they consume minimally processed plant foods. Vegetarians do not consume meat, and vegans also avoid milk, butter, and dairy.
- Lower Cholesterol Levels: Beef, lamb, and pork contain high levels of saturated fat and cholesterol and minimal amounts of polyunsaturated fats; even lean cuts of beef may contain up to 4.5 g of saturated fat per 100 g serving. One-cup serving of whole milk contains 4.5 g of saturated fat, and one tablespoon of butter contains 102 kcal and 7 g of saturated fat. In contrast, one tablespoon of olive oil contains 119 kcal and only 1.9 g of saturated fatty acids.
- Weight Management: Vegetarians, and especially vegans, tend to have lower body weights than omnivores. Although consuming a vegetarian diet does not require counting calories, results from clinical trials demonstrate that people randomized to a vegetarian diet tend to lose more weight than those consuming Western diets.
- Improved Satiety and Blood Sugar Control: The high-fibre and water content and lower energy density of vegetables, legumes, and whole grains may in part explain this effect. Consumption of diets rich in dietary fibre induces gastric distention, delays gastric emptying, and prevents large fluctuations in postprandial blood glucose.
- Beneficial Gut Microbiome: Diet composition has a pervasive effect in modulating systemic microbiome biology.
- Reduced Risk of Type 2 Diabetes: Several studies suggest protective effects of vegetarian diets in the prevention of T2DM.
Risks and Considerations of Plant-Based Diets
- Nutrient Deficiencies: Unhealthy vegetarian diets poor in specific nutrients (vitamin B12, iron, zinc, and calcium) and/or rich in highly processed and refined foods increase morbidity and mortality.
- Not Always Healthier: Moreover, not all plant-based foods are equally healthy.
- Inconsistent Evidence for Cardiovascular Benefits: However, subsequent studies suggest that the protective effect against CHD of vegetarian diets seems to be almost exclusively limited to the Seventh-day Adventists, who don’t smoke, don’t drink alcohol, do regular physical activity, and are very religious and socially connected.
- Cancer Risk: Results from the EPIC-Oxford study on a cohort of 65 000 men and women found that the overall cancer risk was 10% lower in vegetarians and 18% lower in vegans than in meat-eaters. However, after correcting for multiple confounding factors, only stomach and haematological cancers were significantly lower, while cervical cancer was 90% higher in vegetarians.
- Quality of Diet Matters: The quality of diet probably plays a major role. The incidence of colon cancer is reduced by 22% among Seventh-day Adventist vegetarians, but not in British vegetarians.
- Limited Data on Cognitive Function: Very little is known about the effects of vegetarian diets on cognitive function and dementia risk.
Important Considerations for Plant-Based Diets
- Appropriate Planning and Supplementation: According to the American and Canadian Dietetic Associations, appropriately planned and supplemented vegan and lacto-ovo vegetarian diets are nutritionally adequate and suitable for individuals in all stages of the life cycle and may provide health benefits in disease prevention and treatment.
- Focus on Minimally Processed Foods: Further mechanistic studies are desirable to understand whether the advantages of healthy, minimally processed vegetarian diets represent an all-or-nothing phenomenon and whether consuming primarily plant-based diets containing small quantities of animal products (e.g. pesco-vegetarian or Mediterranean diets) has beneficial, detrimental, or neutral effects on cardiometabolic health outcomes.
- Consider a "Flexitarian" Approach: The term "flexitarian" describes someone who eats mostly plant-based foods. Plant-forward is a style of eating that includes meat. But meat is not the star of the meal. This kind of healthy eating is key to the Mediterranean diet.
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