Table of Contents > Alternative Modalities > Heart rate variability Print

Heart rate variability


Related terms
Author information
Contributing factors

Related Terms
  • Adequate protein diet, Barry Sears, carbohydrate, diet, fat, low carbohydrate diet, protein.

  • The Zone diet is an unproven dietary regime, which has been popularized by Dr. Barry Sears through sales of his 1995 book, The Zone. Despite claims made in the book, there is little available research to support its overall benefit.
  • The Zone diet is a calorie-restricted diet that provides adequate protein, moderate levels of carbohydrates, essential fats and micronutrients spread through three meals and two snacks that approximately maintain the protein-to-carbohydrate ratio throughout the day.
  • Proponents believe that the Zone diet promotes optimal metabolic efficiency in the body by balancing the hormones insulin and glucagon. Insulin is responsible for converting, in the blood, incoming nutrients into cells. Glucagon regulates glucose in the liver. Overall, the Zone's food plan consists of a dietary intake of 40% carbohydrates, 30% protein and 30% fat.
  • Under this diet, recommended foods include fruits and vegetables (fresh or frozen), oatmeal (whole grain), protein powder (e.g. soybean isolate), chicken, turkey, lean beef, fish, low-fat cottage cheese, soy food, nuts (e.g. almonds, cashews, macademia, pistachios), extra virgin olive oil, natural sweeteners, such as fructose or stevia.

Theory / Evidence
  • Recent research seems to indicate that a low total caloric intake is associated with longer life expectancy. Based on animal studies, animals eating calorie-restricted diets may live 1.5 to 2 times as long as animals eating high-calorie diets. Theoretically, similar effects may occur in humans. The caloric restriction recommended by the Zone diet is below that of the average American and may be of benefit in weight loss and if maintained over decades in increasing life expectancy. On the other hand, athletes in training will likely suffer from decreased performance if restricted to the low calorie diet recommended by the Zone.
  • Despite proposed benefits, currently there are no high quality clinical trials available about the Zone diet or similar diets consisting of the recommended 40% carbohydrates, 30% fat, and 30% protein. The Zone diet is quite complex in terms of caloric restriction, ratio of carbohydrates/protein//fat, spacing of meals, preferential intake of certain fats, and avoidance or inclusion of a few specific foods.


Author information
  • This information has been edited and peer-reviewed by contributors to the Natural Standard Research Collaboration (

  1. Cheuvront SN. The zone diet and athletic performance. Sports Med. 1999;27(4):213-228.
  2. Natural Standard: The Authority on Integrative Medicine.
  3. Sears B. The Zone Diet and athletic performance. Sports Med. 2000;29(4):289-294.

  • Zero Balancing is different from other types of bodywork because it focuses on both body structure and energy flow at the same time.
  • During zero balancing, the client fully dressed. With the client seated, the practitioner first evaluates the torso. Then the patient lies in a supine position on a padded table, similar to those used for massage and physical therapy. The touch used during zero balancing is called "interface," and has been described by clients as pleasing, gentle, and relaxing.
  • During a session, the practitioner works on finding places where energy fields may be obstructed or otherwise disrupted. Zero balancer practitioners pay particular attention to the skeleton, which they believe holds most of the body's energy. Their practice focuses much attention on the spine, shoulder blades, pelvis, hips, sacro-iliac joints, legs and feet, as they systematically travel up the body. After treating the upper body, the practitioner usually progresses again to the lower body for a final look.
  • Practitioners use a technique called fulcrum, which involves using the arms and hands in a specific geometry to help access energy fields and bring the skeleton and joints into balance. Clients generally feel the touch as lifting, bending, pushing, pulling, sliding, and rotating.
  • One session usually takes 30-40 minutes. Practitioners typically recommend at least three sessions, followed up with regular maintenance visits every 2-4 weeks. Zero balancing sessions range from $50 to $100 each.
  • Certification is available for healthcare professionals who complete a combination of education and practice with the Zero Balancing Health Association (ZBHA).

Contributing factors
  • General: Heart rate variability (HRV) is controlled by the autonomic nervous system (ANS), also known as the visceral nervous system. The ANS is part of the peripheral nervous system (PNS). The nerves in the PNS connect various organ systems to the central nervous system (CNS), which includes the brain and spinal cord. The ANS functions at the subconscious level. In addition to controlling heart rate, it controls bodily functions such as sweating, digestion, and breathing. Because the autonomic control of heart rate can reveal abnormal changes in physiological functions, HRV may be very useful in making diagnostic, prognostic, and therapeutic determinations.
  • In addition to pathological (disease) conditions, there are a number of physiological factors in healthy individuals that may affect heart rate variability (HRV). While some of these factors (such as age and genetic makeup) cannot be controlled by individuals, other factors such as lifestyle choices (such as physical activity, smoking, and other lifestyle choices) are modifiable. Therefore, many lifestyle choices may affect HRV and its role in disease outcome.
  • Physiological factors:
  • Breathing: Respiration (breathing) is known to affect HRV. While it is not entirely clear exactly how breathing affects HRV, evidence from research conducted in canines suggests that an autonomous reflex known as the Bainbridge reflex may be involved. Cardiac (heart) reflexes and respiratory activities (such as rib cage movement) are controlled by the central nervous system (CNS), and thus may also affect HRV.
  • Circadian rhythm: The effects of circadian rhythm on HRV have been studied in healthy men and women. HRV varies over a 24-hour period, peaking at night and plateauing during the day.
  • Posture: In healthy subjects, rising from a supine (lying down) position to the upright (standing up) position increases resting heart rate and decreases the frequency of HRV. In the European Project on Genes in Hypertension (EPOGH) study, HRV was found to consistently vary according to posture, independently of other factors.
  • Non-modifiable factors:
  • Age: It has been firmly established that maximal heart rate becomes lower as individuals grow older. Age is known to affect autonomic control of the cardiovascular system, and is a primary factor that may affect HRV. In the European Project on Genes in Hypertension (EPOGH) study, HRV was found to consistently vary with age.
  • Gender: Females, under age 30, tend to have lower HRV than age-matched males. Gender differences in HRV begin to disappear at age 30 and completely disappear by age 50. This may be because as people age, sympathetic activity tends to decline more slowly in males than females.
  • Genetics: HRV has been examined in the Framingham Heart Study, which is a large multigenerational cohort study that began in 1948. Genomic evidence from this study strongly suggests that heart rate and HRV characteristics may be inherited and shared over multiple generations. The genes that appear to be involved include those that control the ANS and certain neural responses (such as those mediated by the cholinergic system).
  • Modifiable lifestyle factors:
  • Physical activity: The ANS controls heart rate changes during physical activity. Regular physical activity decreases heart rate during both rest and exercise in humans. It is still not exactly clear how regular physical training affects HRV. However, in several studies conducted in canines, endurance training (treadmill running) increased HRV and lowered risk for sudden cardiac death due to arrhythmia.
  • Smoking: Smoking is known to harm the cardiovascular system in part by increasing heart rate and reducing HRV. This effect has also been demonstrated in humans and animals exposed to second-hand tobacco smoke, as well as in infants of smoking mothers.
  • Other factors:
  • Medications: Various medications, particularly those with anticholinergic effects (such as tricyclic antidepressants and antispasmodics), are known to reduce HRV. Moreover, stimulants (such as caffeine and nicotine) increase heart rate and decrease HRV. Atenolol (a beta-antagonistic drug) has been shown to reduce HRV while losartan (angiotensin II receptor antagonist) increases HRV.
  • Pollution: Small-particulate air pollution and second-hand cigarette smoke have both been shown to affect the ANS. Increased heart rate and decreased HRV are associated with an increased risk of cardiovascular disease and related death.

Copyright © 2011 Natural Standard (

The information in this monograph is intended for informational purposes only, and is meant to help users better understand health concerns. Information is based on review of scientific research data, historical practice patterns, and clinical experience. This information should not be interpreted as specific medical advice. Users should consult with a qualified healthcare provider for specific questions regarding therapies, diagnosis and/or health conditions, prior to making therapeutic decisions.

62 Marshall St
Rochester, NY 14607
585-454-0343 (fax)
Email Our Store
Driving Directions


Co-op Connections

Follow us on Instagram!

Follow us on Twitter!

Join our Facebook community!

Email newsletter sign up

Email Newsletter Archive
Click here>>

Download The Rutabaga Rap

Rutabaga Rap Archive
Click here>>

About Our Co-op

Current Job Openings
See current openings>>

Top 10 Reasons for Shopping
Learn more>>

Why become an owner?
Learn why>>

Owner Application
Download (pdf)>>

All About Co-ops
Learn more>>

Our Board of Directors
Learn more>>

Global Ends Policy
Learn more>>

Learn more>>

Advertise in Our Newsletter
Learn more>>

Job Application
Download (pdf)>>

Discover your local co-op!