The three components of energy expenditure in which our bodies burn calories: Basal Metabolic rate, Thermic Effect of Food, Non-Exercise Adaptive Thermogenesis (NEAT), and Activity Energy Expenditure.
THE THREE COMPONENTS METABOLISM FOR FAT LOSS SUMMARY
- Cardio vs. Diet for Fat Loss: While diet alone can lead to a decrease in metabolism, with a loss of both fat and muscle, exercise, especially resistance exercise, is more effective at preserving muscle. A study found that a group that reduced calorie intake lost more muscle mass compared to a group that increased exercise to burn the same amount of calories.
- Understanding Energy Balance: Energy balance is governed by the laws of thermodynamics. Weight gain or loss is determined by the balance between caloric intake and expenditure. The article cites an example of a teacher who lost 60 pounds by eating at McDonald’s daily but maintained a caloric deficit.
- Components of Energy Expenditure: The three main components that determine how our bodies burn calories are Basal Metabolic Rate (BMR), Thermic Effect of Food (TEF), and Activity Energy Expenditure (which includes both exercise and non-exercise activities). BMR accounts for the majority of daily calorie burn, representing the energy needed for basic life functions.
- NEAT’s Impact on Obesity: Non-Exercise Activity Thermogenesis (NEAT) refers to the energy expended through non-conscious activities like fidgeting. NEAT can vary significantly among individuals and plays a crucial role in weight management. Obese individuals tend to have lower NEAT levels than their lean counterparts, which contributes to their weight challenges.
9/28 CARDIO VS DIET FOR FAT LOSS: WHICH IS BETTER?
When trying to lose body fat, most people perform a combination of exercise and calorie restriction. The research is conclusive that diet alone will cause the loss of both fat and muscle, whereas exercise is much better at preserving muscle, especially resistance exercise.
Few studies have compared a direct comparison of a daily reduction in calories from diet alone to increasing exercise daily to burn more calories. In general, it’s much easier to create a caloric deficit by diet compared to increasing the number of calories burned by exercise. For example, cutting calories by 500 is easier than doing cardio to burn 500 calories, as this is more fatiguing. Researchers took overweight males and compared two forms of weight loss.
One group cut calories by 700 calories per day but did not exercise. The diet comprised 55-60% carbohydrates, 15-20% protein, and 20-25% fat. The other group maintained their normal caloric balance but exercised to burn 700 calories daily for 12 weeks. The caloric deficit was created entirely by increasing energy expenditure thru exercise.
The average time spent on the treadmill was 60 minutes per day at an exercise intensity just below 80% of the maximum heart rate. At the end of the study, both groups lost an identical amount of weight, roughly 17 pounds for the diet-only group and 16 pounds for the exercise-only group (i.e., 8% of their total weight), but the composition of the weight loss was dramatically different.
RESULTS
The cardio-only group lost -4.3% of body fat, while the diet-only group lost -3.4%. The cardio-only group lost less muscle mass (-2.2 pounds) compared to the diet-only group (-4.8 pounds). A direct comparison is more revealing as the diet-only group lost 70% of their body fat from fat and 30% from muscle. Conversely, the cardio-only group lost 85% of their weight from fat and only 15% from muscle.
The diet-only group also had a bigger drop in their resting energy expenditure because they lost more muscle. The diet-only group resting energy expenditure dropped by -211 calories, while the cardio-only group had a drop in resting energy expenditure by -126 calories. This means the diet-only group had a 40% greater drop in resting energy expenditure than the cardio-only group.(45)
The study suggests that although it is easier to create a deficit by diet, adding exercise is a better way to burn fat and preserve muscle. It makes sense to cut back on calories and increase energy expenditure thru exercise to create a deficit. However, as the study proves, it is possible to increase fat loss thru exercise alone. What would have been more appealing if they made a direct comparison with resistance exercise, which would have resulted in less lean muscle mass loss? It should be mentioned that cardio is just a tool for fat loss; you can either do more and eat less or a combination of both, which is much easier. You can skip cardio, do resistance exercises, and cut back on calories.
UNDERSTANDING ENERGY BALANCE
Energy balance is based on laws of thermodynamics, whereby energy cannot be created or destroyed; it can only be transformed from one form to another (i.e., gain or lose weight). Gaining or losing weight is a function of “tipping the balance” on the energy balance scale, favoring caloric excess or caloric deficit.
The reason the teacher who ate at McDonald’s every day for 90 days and still lost 60 pounds is a function of being in an energy deficit. (1) He ate two Egg White Delights, a bowl of oatmeal, and 1 percent milk for breakfast. He alternated between a Southwest Salad or Bacon Ranch Salad for lunch with fruit parfait and apple slices. For dinner, he ate a value meal. He ate a small serving of fries just about every day. He calculated his daily caloric needs and ate below his daily energy expenditure. This is not magic; he just ate in a caloric deficit. He probably lost a ton of muscle, but it’s proof of the concept that you must be in a caloric deficit to lose weight.
Humans are well-equipped to store fat. The human body has a remarkable capacity to sense a caloric deficit. Your body has no desire to get lean or lose body fat. Our bodies are better equipped to replace lost weight and rapidly sense a caloric deficit. Energy compensation is more likely when you reduce rather than increase energy consumption.
THE THREE COMPONENTS METABOLISM FOR FAT LOSS
For example, the classic study on energy compensation lasted 14 days; subjects were blind to the number of calories they consumed. The great thing about this study was it was carried out in a metabolic laboratory, so the researchers knew exactly how many calories they were consuming. The researchers secretly replaced their food with lower-calorie, lower-fat foods. For example, the low-calorie replacement replaced their regular soda of 192 calories with a Diet Cola with 4 calories. The subjects could eat as much as they wanted. Despite the caloric replacement of lower-calorie foods, which resulted in a 500 caloric deficit; however, the subjects ate more of their regular food and overcompensated for the reduced-calorie foods.
Thus, the subjects completely compensated for the calorie loss and upregulated calories accordingly to maintain body weight. (2) Similarly, Drenowatz (2015) acknowledged that humans are better equipped to replace lost weight than avoid weight gain, although the phenomenon is characterized by individual variability.(3) Thus, replacing regular foods with fat-free foods may not be the answer to long-term weight loss. Despite the development of fat-free, low-fat, and “lite” foods, obesity has increased.
There are three major components of energy intake: protein, carbohydrates, fat, and alcohol.
Macronutrient Calories
Protein 4 calories
Carbohydrates 4 calories
Fats 9 calories
Alcohol 7 calories
A negative energy balance (i.e., fewer calories consumed) must be established via a smaller energy intake or increased energy expenditure for weight loss to occur. Your body likes to maintain weight, so a complex signaling pathway will drive you to consume more calories. For example, decreasing calories will reduce metabolic rate (i.e., lowering calories burned at rest) and reduce physical activity. (4)
The diverse arrange of physiological consequences that can occur during weight loss depends on: a.) the severity of the caloric restriction .b) the duration of the energy restriction, c.) body composition at baseline, d.) the social environment in which the diet occurs. (5) It was found that eating in the presence of a friend increased caloric intake by 44%, and eating with six others increased caloric intake by 77%.(6)
THE THREE COMPONENTS METABOLISM FOR FAT LOSS
An increase in energy expenditure (i.e., increased exercise or physical activity) will increase appetite signaling hormones, driving you to eat more calories. (7) The appetite response to exercise is highly variable, with some people over-compensating while others were under-compensating. The biological response that drives appetite during caloric restriction is complex. It has been found that for every 2.2 pounds lost, there is an increase in caloric intake by 100 calories. (8)
A J-shaped curve was observed in a meta-analysis of 28 studies comparing the relationship between energy intake and physical activity levels. Cross-sectional studies of low, medium, high, and very high physical activity levels found that the most active individuals consumed the highest amount of calories. (9) The body is trying to maintain homeostasis or its current biological set point in response to dynamic fluctuations in energy expenditure.
COMPONENTS OF ENERGY EXPENDITURE: BMR VS RMR
The three components of energy expenditure in which our bodies burn calories: Basal Metabolic rate, Thermic Effect of Food, Non-Exercise Adaptive Thermogenesis (NEAT), and Activity Energy Expenditure.
Basal Metabolic Rate (BMR):
BMR primarily burns the majority of your daily calories. It constitutes approximately 60% of your overall metabolic rate. If you spent the entire day lying in bed, BMR would represent the number of calories you burn performing basic life functions.
BMR provides the calories required to maintain basic physiological systems such as heart contractions, muscle mass, cell functions, respiration, body temperature regulation, circulation, and nutrient processing.
Professionals conduct BMR measurements in a darkened room after the subject has slept for eight hours and fasted for 12 hours. This setup ensures the digestive system remains inactive and the individual rests in a reclined position for accurate measurements.
RMR MEANING RESTING METABOLIC RATE (RMR):
RMR and BMR share similarities, but professionals measure RMR under less stringent conditions than BMR. Unlike BMR measurements, RMR does not necessitate the subject to sleep overnight in the testing facility. RMR varies significantly between individuals. RMR values can exceed BMR by 3-10%.
Research has shown that RMR does not impact weight loss success or predict future weight gain. Adults with low BMRs did not gain more weight than those with high BMRs, implying that caloric intake or activity are the primary factors for weight gain. (10) Obese people can often have higher resting metabolic rates than their non-obese counterparts. When body composition (i.e., fat-free mass) is taken into account, these differences between obese and non-obese individuals disappear, suggesting that metabolism in obese individuals is not altered. (11) REE is mostly determined by body size and composition and positively correlates with body weight and fat-free mass.
The fat-free mass has a major contributing factor when calculating total daily energy expenditure. Lean mass contributes about 60–70% of a person’s RMR, whereas fat mass accounts for as little as 5– 7%. (12) On average, 1 kg of fat tissue expends ~4.5 kilocalories (kcal) per day at rest (i.e., 4.5 kcal/kg/day), whereas 1 kg of skeletal muscle expends ~13 kcal/kg/day at rest. (13) Researchers tracked the participants in the Biggest Loser Show, and many of them had regained weight. A 21% decrease in total energy expenditure occurred in the Biggest Loser study; RMR per kilogram of lean mass decreased by 504 calories per day, indicating lean mass has a profound impact on metabolic rate. (14)
DOES YOUR METABOLISM DROP AFTER AGE 30?
It has long been suspected that metabolic rate declines after 30. How often have you heard, “My metabolism is like it was in my 20s!” In the prestigious Journal of Science, researchers tracked the metabolism of 6,742 participants, both males, and females. They used a wide range of ages, from babies to older adults in their 90s in 29 countries. Researchers looked at the components of resting metabolism and measured total daily energy expenditure, fat-free mass or lean mass, fat mass, and body weight.
They measured the metabolic rate of organs, with the metabolic rate being the highest in the heart, liver, kidney, and brain (~60%). They used doubly labeled water, the gold standard for measuring energy expenditure. The authors found that total and basal metabolic rates increased with fat-free mass. Lean muscle mass accounted for 83% of the variation in metabolism. Infants (i.e., 9-15 months of age) were at the peak of the metabolic chart, with their bodies burning 50% more calories than an adult. The big surprise was that metabolic rate did not change between ages 20 to 60. The data showed that after age 60, there is a gradual decline in metabolism of about .07% per year. (15) So technically, your metabolism does slow down, but it’s not until after age 60!
Thermic Effect of Food (TEF):
TEF, or dietary-induced thermogenesis, increases metabolism after a meal and accounts for approximately 10% of total energy expenditure. It represents the energy expenditure of processing and storing food and the metabolic effects of the influx of nutrients. TEF is the energy required for digestion, absorption, usage, and storage of nutrients. Age, physical activity, meal size, composition, frequency, and timing influence TEF.(16)
High-protein meals have been found to have a greater TEF than carbohydrate and fat meals. The measured thermic effect of different nutrients is highest and most prolonged for protein (20–30%), followed by carbohydrate (5–10%) and fat (0–3%). (17) DIT is higher in the morning compared to the evening. (18) Besides meal timing, DIT is also influenced by the number of calories in the meal and increases in direct proportion to the energy intake. (19)
TEF: PROTEIN > CARBOHYDRATE > FAT
Many factors can contribute to DIT, including meal size, macronutrient composition (i.e., protein having the greatest effect), frequency of meals (i.e., smaller DIT for smaller frequent meals than one large meal), types of fats (i.e., Medium-Chain Triglycerides having a greater effect than Long-Chain Triglycerides), etc.
A conclusive meta-analysis reported that for every 24 calories increase in energy intake, DIT increased by .3 calories per hour. The article also found that high protein or carbohydrate meals had a higher DIT than high fat, although this effect was not always significant. (20)
Activity-related energy expenditure (AEE)
AEE is the number of calories burned during movement and physical activity. AEE is further divided into exercise and non-exercise activity thermogenesis.
EXERCISE INDUCED THERMOGENESIS: EID is defined as planned, structured, and repetitive physical activity that has the aim of improving health (for example, sports, and visiting the gym). This is the number of calories burned during exercise. Going to the gym, running, etc. It’s a conscious act of trying to burn calories.
NON-EXERCISE INDUCED THERMOGENESIS (NEAT): NEAT is the amount of energy spent through non-conscious activity such as fidgeting, tapping your leg, typing on a computer, etc. NEAT has also been referred to as Non-Exercise Physical Activity. The number of calories burned thru NEAT can vary considerably among people ranging from 15% of the total daily energy expenditure in sedentary people to 50% or more daily energy expenditure in highly active people. Urban societies which have the luxury of cars, dishwashers, and washing machines all result in decreased NEAT levels. (21)
NEAT can vary as much as 2000 calories per day between individuals with similar body composition, gender, and age. (22) NEAT is also related to genetics; some people are genetically more prone to fidgeting and have higher NEAT levels. Very low physical activity levels, such as fidgeting, can increase energy expenditure above resting levels by 20–40%.
NEAT AND METABOLISM
NEAT has been found to increase during an energy surplus and decrease while in a caloric deficit. (23) The variability in NEAT is predictive of weight gain during overfeeding. For example, one study found that those individuals who increased their NEAT during overfeeding gained the least amount of body fat; conversely, those that failed to increase their NEAT gained body fat. (24) Some have tried to increase NEAT activity by using standing desks and seated foot pedaling. One study compared sitting, standing, and seated foot-pedaling devices. The seated foot pedaling device elevated metabolic rate by 17.6% compared to sitting and 7% compared to standing. (25)
Another study found that a walking treadmill where people worked for 2.5 hours per day had beneficial effects on body composition and increased overall activity with a decrease in NEAT. (26) When lean individuals’ NEAT levels were compared to obese individuals, the obese individuals were seated for two hours longer than lean individuals. If obese individuals were to adopt the practices of lean individuals, they could burn an additional 350 calories per day. (27)
[TDEE MEANING] TOTAL DAILY ENERGY EXPENDITURE = BMR + NEAT + EXERCISE +TEF
EXERCISE VS NEAT: WHAT BURNS MORE CALORIES?
Most people believe that exercise is a better way to burn calories, but it’s just the opposite. NEAT’s energy expenditure is much larger than exercise when measured over the day. (28) It has been reported that 85-90% of the diet-related decrease in total energy expenditure is due to NEAT. (29) It has been found that long-term weight loss may be easier by focusing less on exercise calories burned and more on increasing NEAT. (30)
Low-intensity activities over a greater duration result in greater calories burned than short bursts of high-intensity physical activities. Researchers tracked low-intensity, moderate-intensity (walking and cycling), and high-intensity in this study. Those who reported high-intensity exercise reported lower physical activity throughout the day than moderate intensity.
METABOLISM STUDIES
It is suspected that the higher metabolic cost of high-intensity exercise resulted in a reduction in energy spent on physical activity outside of training. (31) A similar study in obese adolescents that performed high-intensity cycling for 30 minutes had a decrease in NEAT, whereas normal-weight adolescents had no decrease in NEAT.(32)
Resistance exercise has been found to preserve NEAT compared to aerobic exercise. (33) Aerobic exercise burned more calories during exercise compared to the resistance exercise group. Resistance exercise increased NEAT levels by 216 calories per day, whereas aerobic exercise decreased NEAT levels by 148 calories per day. Aerobic exercise leads to greater fatigue, resulting in a greater reduction in physical activity outside of exercise. (34)
One study reported a dose-dependent attenuation of predicted weight loss with increasing amounts of aerobic exercise in overweight and obese postmenopausal women. (35) In a study that compared moderate exercise (i.e., 30 minutes, 300 calories burned) to high-intensity exercise (i.e., 60 minutes, 600 calories burned), both groups lost similar weight and body fat. So despite doubling the aerobic exercise dose, there were no further changes in fat loss or weight loss. NEAT also increased by 37% in the moderate exercise group. (36)
It should be mentioned that the NEAT response to exercise is highly variable among people. Some people increase their NEAT in response to exercise, whereas others decrease their NEAT. If you are a personal trainer, if weight loss is your client’s goal, having them wear a step counter can be a valuable insight into increasing total daily energy expenditure outside of the gym.
WAYS TO INCREASE NEAT
- Stand Up More Often and Move Around
- Take the stairs instead of the escalator
- Park further away from a destination and walk further. Get your daily step count up.
- Do more household chores such as cutting the grass, laundry, etc
METABOLISM AND NEAT HAS A MAJOR IMPACT ON OBESITY
As discussed previously, obesity is not the result of slow metabolism; in fact, obese people tend to have a higher energy expenditure just to their larger size. One major finding is that obese people have a much lower NEAT level than normal-weight people. Researchers compared NEAT levels of 10 lean women and 10 obese women for two weeks. The resting metabolic rate was higher in obese women, as expected, but the big difference was the NEAT levels.
NEAT levels were much lower in obese women, translating to about 400 calories per day. Obese women were found to spend more time resting (53% vs. 42% for lean women), stood less (11% vs. 20% for lean women), and performed less physical activity than normal-weight women (6,970 steps per day vs. 11,393 steps per day). This was not related to exercise, as both groups were not involved in any exercise program per se. (37)
NEAT AND METABOLISM STUDIES
NEAT also has a major contributing factor to weight loss. During caloric restriction, there is a drop in NEAT. In one study, those who lost 10% of their body weight decreased NEAT by 400 calories compared to control subjects. (38) In another more extreme weight loss study, when subjects lost 23.2% of their body weight resulted in a decrease in physical activity level that corresponded to 582 calories per day or 71% of the decrease in 24-hour energy expenditure. (39)
Fat loss is hard! Your body fights you to stop losing body fat and encourages future weight gain. One would think that it would be a simple process because we have so many fat cells. A lean adult has 35 billion adipocytes, totaling 130,000 kcal of stored energy. An extremely obese adult can have 140 billion, totaling 1 million kcal stored energy. (40) The longest-ever medically supervised starvation period in history was 382 days, in which a 27-year-old man went from 455 pounds to 180 pounds. (41)
Once calories are reduced, our bodies send off a cascade of events to increase appetite, slow fat metabolism and reduce energy expenditure. Your body’s fat thermostat, a hormone called leptin, drops and slows the number of calories you burn. Leptin is a powerful regulator of appetite; when fat cells shrink and less leptin is secreted, it signals to the brain to increase appetite. (42) Leptin concentrations are controlled by body fat and food availability. (43) Appetite plays a larger role in controlling fat loss than metabolism. It has been found that for every 20-30 kcal per day increase, appetite will increase by about 100 kcal per day above the prior weight loss. (44)
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