Why a Calorie-Restricted Diet?
According to a widely cited study published in the journal Cell Metabolism in May 2018, cutting just 15 percent of your calorie intake can slow aging and cause significant weight loss in as little as two years. Subjects who ate 15 percent fewer calories for 24 months dropped 17.6 pounds and experienced a major reduction in oxidative stress markers. As the researchers point out, calorie restriction reduces energy expenditure, leading to a longer life.
Calorie-restricted diets support health and well-being, with benefits that go beyond fat loss. When you cut calories over the long-term, your body becomes more efficient at utilizing energy. Fat, for instance, is used for fuel rather than stored in adipose tissues.
Another study, featured in the American Journal of Clinical Nutrition in February 2017, found that restricting calories by 25 percent over two years can decrease fat mass and waist circumference, increase lean body mass and improve cardiometabolic health in nonobese adults.
The study participants lost about 11 percent of their weight after one year and 10 percent (compared to their initial body weight) after two years of calorie restriction. Men lost significantly more fat than women (28 versus 38 percent). These findings indicate that a calorie-restricted diet not only facilitates weight loss but also improves body composition aka muscle-to-fat ratio.
Furthermore, it may help reduce blood pressure, blood sugar levels and inflammatory markers in people with diabetes, according to a January 2017 clinical trial published in Diabetes. By the end of the study, diabetic subjects who reduced their calorie intake had lower bad cholesterol levels, higher good cholesterol levels and decreased blood pressure.
Examples of Calorie-Restricted Diets
Ever heard of the 5:2 diet plan? What about the Warrior diet? These are just two examples of calorie-restricted diets. Depending on your preferences and how much weight you want to lose, you can also try alternate-day fasting, periodic fasting or time-restricted feeding.
Any weight loss plan that limits your daily calorie intake falls into this category. For example, if you normally consume 2,500 calories per day and then switch to a 1,200-calorie diet, you're basically restricting your calorie intake. Some diet plans, though, are less flexible than others. A 500-calorie meal plan, for example, can affect your health and cause severe nutrient deficiencies.
In general, crash diets are extremely low in calories. These weight loss plans provide only temporary results and may result in kidney damage, abnormal heart rate, dehydration and electrolyte imbalances, as Penn Medicine points out.
As mentioned above, calorie restriction is beneficial. However, the diet plans used in clinical trials are nutritionally sound and have nothing in common with extremely limited diets such as the cabbage soup diet, the lemonade diet or the feeding tube diet.
Take the Warrior diet, for example. This dietary pattern is largely based on intermittent fasting, meaning it involves periods of little or no food intake followed by periods of feeding. Dieters must abstain from food for 20 hours a day and eat within a four-hour window at night. Proponents say that this is how humans ate millions of years ago.
Unfortunately, no studies have been conducted on the Warrior diet. However, there is plenty of evidence to support the health benefits of intermittent fasting (IF) and food restriction.
According to a review published in Proceedings of the Nutrition Society in August 2017, IF may trigger metabolic changes that lead to weight loss and reduce ectopic fat, which consists of fatty deposits in or around the liver, heart, kidneys, muscles and other organs and tissues. This type of fat has been linked to a greater risk of inflammation, insulin resistance, cardiac events and impaired kidney function.
Another research paper featured in the International Journal of Obesity in December 2014 suggests that popular IF protocols, such as the 5:2 diet plan, facilitate weight loss by reducing total food intake. The downside is that fasting increases hunger, so you might end up eating more and quit dieting altogether. Daily calorie restriction is more sustainable in the long run and may have better health outcomes.
How to Plan Your Meals
Whether you opt for daily calorie restriction or intermittent fasting, the key to weight loss is to create a calorie deficit. Basically, you need to either burn more calories than you take in or eat fewer calories than you burn.
As the Mayo Clinic notes, one pound of fat equals 3,500 calories (this number isn't set in stone, though). This means that if you cut 3,500 calories from your daily meals or burn 3,500 calories through exercise, you'll lose one pound.
Try to determine your current energy intake. For example, if your diet provides 2,000 calories per day, that's 14,000 calories per week. To lose two pounds per week, it's necessary to cut out 7,000 calories. Therefore, you must switch to a 1,000-calorie diet and plan your meals accordingly.
Here's one trick you can use: Fill up on foods that are high in water, fiber or protein. Cucumbers, for example, are over 95 percent water and have just 8 calories per cup, so enjoy them anytime without having to worry about your weight. Protein-rich foods, such as turkey breast, tuna and eggs, increase satiety and may improve body composition, while fiber keeps you full longer.
Nuts, seeds, olive oil and other nutrient-dense foods are healthy and full of flavor. The downside is that they're high in calories. Pistachios, for instance, boast 159 calories per serving (1 oz). Most people eat a lot more than just one serving at once, so the calories can add up quickly.
A calorie-restricted diet will consist mostly of veggies, low-fat dairy, lean meat, fish, berries and eggs. These foods are low in calories and have a satiating effect. A 1,000-calorie meal plan could look like this:
- Roasted chicken breast (3.5 oz): 107 calories, 21.4 grams of protein and 0.8 grams of fat
- 1 medium sweet potato: 115 calories, 2 grams of protein, 0.2 grams of fat, 26.7 grams of carbs and
3.8 grams of fiber
- Chopped salad blend (2.9 oz): 25 calories, 2 grams of protein, 5 grams of carbs and 2 grams of fiber
This meal plan provides approximately 996 calories, 92.4 grams of protein, 34.2 grams of fat, 78.8 grams of carbs and 21 grams of fiber (consider taking psyllium husk to boost your fiber intake). Due to its high protein content, it will help you preserve lean mass while on a diet. Season your meals with herbs, spices or pickles for extra flavor.
While you may lose weight limiting your intake to 1,000 calories a day, this may be too few calories and place you at risk of nutritional deficiencies. The National Heart, Lung and Blood Institute says men shouldn't eat fewer than 1,500 calories a day and women no less than 1,200 calories. Consult with your doctor before starting and calorie-restricted diet.
- Harvard T.H. Chan School of Public Health: "The Best Diet: Quality Counts"
- Cell Metabolism: "Metabolic Slowing and Reduced Oxidative Damage With Sustained Caloric Restriction Support the Rate of Living and Oxidative Damage Theories of Aging"
- The American Journal of Clinical Nutrition: "Body-Composition Changes in the Comprehensive Assessment of Long-Term Effects of Reducing Intake of Energy (CALERIE)-2 Study: A 2-Y Randomized Controlled Trial of Calorie Restriction in Nonobese Humans"
- Diabetes Journals: "Renal and Systemic Effects of Calorie Restriction in Patients With Type 2 Diabetes With Abdominal Obesity: A Randomized Controlled Trial"
- Penn Medicine: "Want to Lose Weight Quickly? Here Are 7 Reasons Why Crash Diets Probably Won’t Work"
- Proceedings of the Nutrition Society: "Effects of Intermittent Fasting on Glucose and Lipid Metabolism"
- Endocrinology and Metabolism: "Ectopic Fat Assessment Focusing on Cardiometabolic and Renal Risk"
- International Journal of Obesity: "Fasting for Weight Loss: An Effective Strategy or Latest Dieting Trend?"
- NCBI: JAMA Internal Medicine: "Effect of Alternate-Day Fasting on Weight Loss, Weight Maintenance, and Cardioprotection Among Metabolically Healthy Obese Adults: A Randomized Clinical Trial"
- Mayo Clinic: "Counting Calories: Get Back to Weight-Loss Basics"
- USDA: "Cucumbers"
- British Journal of Nutrition: "Dietary Protein – Its Role in Satiety, Energetics, Weight Loss and Health"
- Joslin Diabetes Center: "How Does Fiber Affect Blood Glucose Levels?"
- USDA: "Pistachios"
- USDA: "Hard-Boiled Eggs"
- USDA: "Bananas"
- USDA: "Cottage Cheese"
- USDA: "Roasted Chicken Breast"
- USDA: "Sweet Potatoes"
- USDA: "Chopped Salad Blend"
- USDA: "Low-Fat Greek Yogurt"
- USDA: "Almonds"
- USDA: "Cooked Wild Salmon"
- USDA: "Cooked Kale"
- NCBI: Advances in Nutrition: "Preserving Healthy Muscle During Weight Loss"
- National Heart, Lung and Blood Institute: "Healthy Eating Plan"