Metabolism: Bust the Myths (Part 2)

Reyna F

This is Part 2 of a two part blog post on metabolism. Part 1 explained RMR/BMR and how to determine these factors (click here).  Part 2 explains what will and will not impact metabolism.

Part 2 is written in a myth-busting format since I get so many interesting questions regarding how to increase metabolism.  See how many True/False questions you get right!



Your body burns more calories digesting ice cold beverages and foods (T/F)

True. But the small difference in calories probably won't make a significant dent in your diet. Different studies have suggested that five or six ice-cold glasses of water could help you burn about 10 extra calories a day equaling about 1 pound of weight loss each year.

Drinking the right amount of water can help you burn more calories (T/F)

True. There are 2 theories:

1.  All of your body's chemical reactions, including your metabolism, depend on water. If you are dehydrated, you may be burning up to 2% fewer calories, according to researchers at the University of Utah who monitored the metabolic rates of 10 adults as they drank varying amounts of water per day. In the study, those who drank either eight or twelve 8-oz glasses of water a day had higher metabolic rates than those who had four.

2.  In 2003, an article was published in the Journal of Clinical Endocrinology and Metabolism. It spoke of a study involving seven healthy men and seven healthy women. All participants were of normal weight. Each participant consumed 500 ml of water per day (a half-liter or about a pint). When their metabolic rates were measured, the researchers found that all metabolic rates were increased by roughly 30 percent. This spike in the metabolism, according to the study, occurred quickly after water consumption: the metabolism was at its greatest spike within a half an hour and was maintained for more than an hour. In that time they burned an extra 25 calories.

What is the reason for this? Researchers theorized that most of the effect comes from warming the water in the stomach. In the male participants, the calories came mostly from stored fat, in the women it came from stored carbohydrates. The water enters the body cold and must be warmed up in the stomach. This "warming up" causes the body's metabolism to increase briefly.  This study further substantiates the idea that ice water, in particular, can help burn calories. Just as the researchers stated above, the ice water in your system must be warmed up by your body. It goes in cold, but when it exits it's no longer freezing. The conversion from ice water to warm water burns calories.

Dieting drops your resting metabolic rate, making it harder to keep weight off (T/F)

True. For every pound you lose, your resting metabolism drops by about 2 to 10 calories a day. Lose 10 pounds, and you now have to eat 20 to 100 fewer calories to maintain your trimmer physique, not factoring in exercise. However, you can prevent your metabolic rate from slipping while you get slim. One way is to lose fat but maintain muscle. You can do this by reducing calories and increasing aerobic and resistance exercise.

Hot foods will fire up metabolism (T/F)

True. While capsaicin is often linked to an increased metabolic rate, specific information varies by study.

ü  In 2008, a study published in the Journal of Biological Chemistry indicated that "the consumption of [capsaicin] is linked with increased metabolic rate and core body temperature." The study found the active chemical in peppers can directly induce thermogenesis, the process by which cells convert energy into heat.

ü  Another study reports that about 1 tbsp. or 30 milligrams of capsaicin, or one tablespoon of chopped red or green chili pepper, has been shown to temporarily boost metabolism by 23 percent.

ü  Stanford University claims that there could be as much as a "50 percent increase in metabolism for three hours after eating capsaicin."

ü  Other reports indicate that an increase may be as negligible as less than 10 percent.

Eating more protein will rev up your metabolism (T/F)   

True. Evidence exists that protein exerts an increased thermic effect when compared to fat and carbohydrate. Evidence is also convincing that higher protein diets increase satiety when compared to lower protein diets. In general, the typical thermic effect of protein is 20% – 35% of energy consumed, and for carbohydrate this number usually falls between 5% –15%.

The thermic effect of fat is a subject of debate. Some have found that fat has a lower thermic effect compared to carbohydrate, while others have found no difference between the two. A main reason for the difference in the thermic effects of food may be due to the fact that the body has no storage capacity for protein and thus it needs to be metabolically processed immediately. The synthesis of protein, the high ATP cost of peptide bond synthesis as well as the high cost of urea production and gluconeogenesis are often cited reasons for the higher thermic effect of protein.

Eating a grapefruit before every meal speeds metabolism (T/F)

False. Grapefruit won't work miracles for your metabolism, but it can help you lose weight. Half a grapefruit before meals helped individuals lose about 4 pounds in 12 weeks, according to a study published in the Journal of Medicinal Food. The reason: its fiber and water fill you up on fewer calories, so you eat less at your next meal. 

Celery is a "negative calorie food" because digesting it uses up more calories than it provides (T/F)

False. The thermal effect of food (TEF) causes the body to burn calories as it processes food. But this process accounts for anywhere from 0 to 30% of the calories consumed. A medium size rib of celery has about 6 calories; its TEF is approximately 1/2 a calorie.

If you have limited time, exercise at a higher intensity for a metabolic after-burn. (T/F)

True. The exercise after-burn, or the calories expended (above resting values) after an exercise bout, is referred to as ‘excess post-exercise oxygen consumption’ or EPOC. This represents the oxygen consumption above resting level that the body is utilizing to return itself to its pre-exercise state.

The physiological mechanisms responsible for this increased metabolism include the replenishment of oxygen stores, phosphagen (ATP-PC) resynthesis, lactate removal, and the increased ventilation, blood circulation and body temperature above pre-exercise levels. Studies have found that the magnitude and duration of EPOC is dependent on the intensity and duration of exercise. It generally takes anywhere from 15 minutes to 48 hours for the body to fully recover to a resting state. Other factors influencing EPOC include training status and gender.

Lifting weights boosts your metabolism more than a cardio workout (T/F)

False.  Leading exercise physiologists conducted a comprehensive review of the research on exercise and weight loss for the American College of Sports. While resistance training was recommended for its beneficial role in potentially improving muscle, strength and power, they found no evidence that it enhanced weight loss, especially when combined with dieting.

A common claim is that every extra pound of muscle burns from 30 to 50 calories per day. Some sources cite that one pound of muscle can burn an extra 100 calories per day.   In reality, one pound of muscle burns about 7 to 15 calories a day.

A high-intensity workout that combines weight training and cardio without any breaks will raise your heart rate, burn the most calories and provide the longest sustained metabolic boost--though it won't have a permanent effect on your RMR. The increase in metabolism is due to the increased excess post-exercise oxygen consumption (EPOC) which some people call the “after-burn”.  EPOC is the total oxygen consumed after exercise in excess of a pre-exercise baseline level. The greater the EPOC, the longer you will burn calories.  Incorporate high intensity interval training (HIIT) and sprints for the increased “afterburn.”

PMS cravings are related to the boost in metabolism before your period (T/F)

Studies do not agree: One theory states that our resting metabolic rate may increase during the luteal phase of the menstrual cycle (the day after ovulation to the first day of your period). The metabolic boost can equal as much as 300 calories a day which is why our appetite increases during this phase.

But another study indicates metabolic rate and calorie expenditure do not increase during that time of the month. What does happen is a change in hormones that cause an increase in appetite to prepare the woman's body for pregnancy and to increase weight.

Green Tea boosts metabolism (T/F)

Possibly. Green tea is one of the most common herbal supplements that is being added to thermogenic products because it has been suggested to affect weight loss and is now the fourth most commonly used dietary supplement in the U.S. Green tea contains high amounts of caffeine and catechin polyphenols. The primary catechin that is associated with the potential effects on weight loss through diet induced thermogenesis is the catechin epigallocatechin gallate, also known as EGCG.

• Dulloo et al reported that green tea supplementation in combination with caffeine (e.g., 50 mg caffeine and 90 mg epigallocatechin gallate taken 3-times per day) significantly increased 24-hour energy expenditure and fat utilization in humans to a much greater extent than when an equivalent amount of caffeine was evaluated suggesting a synergistic effect. 
• Research by Di Pierro and colleagues reported that the addition of a green tea extract to a hypocaloric diet resulted in a significant increase in weight loss (14 kg vs. 5 kg) versus a hypocaloric diet alone over a 90 day clinical trial.
• Maki and coworkers also demonstrated that green tea catechin consumption enhanced the exercise-induced changes in abdominal fat.

Green tea has been theorized to increase energy expenditure by stimulating brown adipose tissue thermogenesis.  Note there are also human and animal studies that have not supported these findings and have reported that supplementation of these extracts does not affect weight loss.

What can you do to increase your metabolism?

1. Exercise more and/or add interval training and sprints into your weekly workouts. 
2. Add chili pepper and turmeric to food, and drink green tea.
3. Include weight training to maintain or build muscle mass, but include cardio for weight loss and wellness.
4. Avoid products that are “metabolism boosters” since they are not regulated and there are possible risks associated with these products. And once you stop using them, you end up gaining the weight back.

References:

• American Journal of Clinical Nutrition
• Journal of Applied Physiology
• Journal of Biological Chemistry
• Journal of the American College of Nutrition
• Journal of the Academy for Nutrition and Dietetics
• Journal of the International Society of Sports Nutrition

For more information, contact Reyna Franco (Reyna@reynafranco.com). She is a registered dietitian, certified personal trainer, certified specialist in sports dietetics and NY Flyers member.  Her office is located on the upper west side and she counsels individuals and groups on sports and medical nutrition.  Her new and improved website is www.reynafranco.com.