hello and welcome to this lecture on energy balance energy balance occurs when the energy so the calories that you intake equal the amount of calories that you expend your body weight tends to be stable during energy balance now you can slip into positive or negative energy balance positive energy balance is when you gain weight because your energy intake is greater than your expenditure so you can see the silhouette she's gotten a little more plump and that's because on the skin scale of energy balance her food intake outweighs that of her exercise on the bottom part of the screen you see negative energy balance this occurs when energy intake is less than energy expenditure body weight tends to decrease during negative energy balance so what we're going to look at during this lecture is what are the different components of both the energy intake more importantly the energy expenditure side of the equation because at this point in the class you already know about where you get calories from a little bit about the relationship between hunger appetite satiation and satiety if you haven't heard those terms satiation and satiety refer refer to the feeling of being full okay now our goal is to be full of nourishing foods so we get enough nutrition but not too much that we feel satisfied but that we don't overdo it or underdo it so let's start in the upper left hand portion at step one the physiological influences okay what are the things that make us feel hungry did you know that actually having an empty stomach causes contractions of your stomach that actually send neurotransmitters to your brain that tell you you're hungry so if you haven't eaten in a long time you don't have any food in your stomach you don't have any nutrients in your small intestine and your bloodstream and so your digestive system starts to trigger hormones and neural signals that create feelings and sensations of hunger and appetite so now we move on to step two sensory influences in addition to just physically feeling hungry there's lots of external things like the smell the sight or the taste of foods that may enhance your desire for them think about when you're walking through the airport and you smell cinnamon Cinnabon cinnamon buns you might not actually be physically hungry but all of a sudden because of the smell especially of the fat cooking and you're walking by it and you got a bunch of time to kill in the airport you all of a sudden feel like you need to eat a cinnamon bun okay those are the sensory influences that work that allow you to seek food start your meal and then we move into the pink box on the lower right where you keep eating because you have cognitive influences you've got the presence of others or social stimulation maybe boredom you're in the airport people eat just because they're bored okay perception of hunger awareness of fullness if you're around your favorite foods okay or foods with special meanings you might be more inclined to eat them even if you're not actually hungry okay the time of day how many times you find yourself eating lunch just because it's 12:00 people who have worked work or office jobs do that a lot might not actually be hungry they just eat because it's 12:00 okay and then we always have the problem of the abundance of available food we live in a 247 food environment where I'm sure no matter where you're listening to this lecture with be 99% of you could go and get food within the next two minutes if you wanted to okay food is constantly around us which causes us to eat more in step four we see the the onset of satiation or the end of a meal okay you have postingestive influences after food enters your digestive tract food in your stomach triggers stretch receptors nutrients in your small intestine then elicit nervous and hormonal signals that inform your brain hey this person's fed stop eating we move on then to step five which is satiety several hours of other activities have passed since you've been eating and you've got other post-absorptive influences after your nutrients have trans gone transferred through your stomach and into your small intestine they get into your blood and Signal your brain about the availability of nutrients how to use them and that they need to be stored as your nutrient status dwindles so does satiety and eventually you'll develop hunger again and then you'll move back into the cycle one more time when we talk about energy balance though it's important to differentiate the difference between appetite and hunger appetite is defined by your desire to consume specific Foods triggered by external Clues cues for example the the smell of food you smell that cinnamon bun and the fat cooking and then you want it that's your appetite at work okay this works independent of hunger Hunger is the actual physical desire to consume food that is triggered by internal physiological signals okay that's when you actually physically feel hungry but you might eat because you physically feel hungry and eat that doughnut to make you not feel hungry or you might eat because your appetite tells you to which is you smell that doughnut okay and all of a sudden you want it on the energy intake side of the equation As A Brief Review you get calories from the following four places fats proteins carbs and alcohol keeping in mind that all excess calories no matter where they're from can be stored as fat your hormones play a role in how much you eat as well to some degree okay and the effect of these aren't really entirely known because many of these hormones have only been discovered recently one of the hormones that helps to regulate appetite and in intake is called leptin leptin is a hormone produced by your fat cells okay now think about that previously it was thought that fat was an inert substance it just sat there and made you fat but we now know that fat is actually metabolically active tissue your fat tissue is sometimes referred to as your adapost tissue and it's constantly secreting hormones neurotransmitters including this hormone called leptin and the role of letin is to help suppress your appetite basically what's supposed to happen is when you've eaten Le should get released to tell your brain hello this person's had enough fat stop eating when people lose weight what happens is they tend to lose or see reduced levels of leptin and their body tends to interpret that as starvation and sometimes why related to why we seeing a slow we see a slowing of the metabolic rate with weight loss okay leptin levels tend to be correlated with the percent body fat in individuals and women have higher concentrations then do men now when leptin was first discovered it was thought well this is going to be genius because what we'll do is we'll just find all the people who are letin deficient and will give them leptin hormone which will suppress their appetite and they won't eat but the problem is most overweight people they're not deficient in leptin they're just resistant to leptin okay so the leptin that they have doesn't really work that much so it appears that overweight and obese people are LEP and res resistant and you can't just trick them by giving leptin so there are all sorts of really cool animal studies that came out once leptin was was understood and was first discovered but they haven't really transferred well into the human space and leptin hasn't been proven to be this weight loss hormone that scientists originally thought it would have been another hormone that plays a role in appetite is grin okay and gin is a hormone that's secreted by your stomach muscles so leptin's made by your fat tissue but grin's made by the cells in your stomach not your tissue from your cells can I sometimes remember growlin you can think of growlin like your stomach is growling okay grin is what makes you feel hungry okay so gin when it's released acts on your hypothalamus which is your hunger Center to stimulate hunger and stimulate food intake gin basically works the opposite of leptin before you eat when you're hungry your gin levels are high and your gin levels decline after you're done eating gin levels tend to be high and people who are lean and low in people who are obese an interesting application of grin is that some of the associated weight loss that comes with gastric bypass or weight loss surgery is thought to be due to the reduction in grin the part of the stomach that secretes grin gets bypassed okay and so these people end up feeling less hungry because the parts of their stomach that secrete grin have been bypassed so they're not in use now let's move to the energy expenditure side of the scale got energy intake and you know where calories come from but how do you get rid of calories there's three basic components the thermic effect of food physical activity and your basil metabolism we'll start with basil metabolism because that counts for the majority of your total energy expenditure okay total energy expenditure is abbreviated te and somewhere about 65% somewhere between 50 and 70% of your total energy expenditure is made up of Basil metabolis ABM it's the basic stuff you need to do to keep yourself alive you actually burn calories doing that now further up the scale you got physical activity this is the energy required for movement and it accounts for anywhere between 15 to 30% of total energy expenditure okay now of course that can vary depending upon whether you exercise more or exercise less lastly and most small most minutely I'm not sure you see the thermic effect of food okay makes the least contribution to your total energy expenditure the thermic effect of food which is sometimes abbreviated TEF is the energy required to process food so when you eat food and you're digesting food it actually Burns some calories okay about 10% of your total energy expenditure so you're burning calories by eating calories if you want to think of it that way now of course your basil metabolism constitutes the greatest amount of energy expenditure but the one over which you have the greatest control is physical activity okay you can increase the amount of physical activity you do thereby increasing the amount of calories you burn and the cool thing about physical activity is not only do you burn more calories when you're actually exercising more but every day of physical activity increases your basil metabolism so if you exercise let's say earlier today or yesterday you are burning more calories if you're sitting on your butt listening to the lecture right now than if you had an exercise you burn more calories at rest meaning your basil metabolism is increased if you engage in more physical activity so physical activity not only helps you burn calories while you're doing the activity it also increases your basil metabolic rate basil metabolism there's a couple of terms that sound similar so I'll spell them out for you here okay basil metabolism is the energy expended to sustain basic life functions okay so you can breathe your heart can beat your nerves can function your muscles can stay functioning as well the basil metabolic rate refers to the amount of energy expended per hour okay somewhere between 50 to 70% of your total energy expenditures made up by your basil metabolism basil energy expenditure refers to what your basil metabolic rate is over the period of 24 hours so basically how many calories did you burn over those 24 hours that's the be what are the different things that affect your basil metabolic rate okay there's you hear people say things that change your metabolism okay as far as your actual metabolic rate as it pertains to weight one of the few things that changes your metabolism is going through menopause okay when women go through menopause they lose hormones that previously had supported higher rates of metabolism and so they end up burning less calories at rest it's why it's extremely important for menopausal women to exercise regularly so that they don't gain weight by eating the same amount of foods that they used to eat a couple other things can affect your basil metabolic rate the greater the percentage of lean body mass you have the higher your basil metabolic rate is it takes more fuel to fuel a pound of muscle than it does to fuel a pound of fat fat doesn't do a whole bunch it just sits there muscle con L working you burn more calories if you're working on muscle than you're working on fat males have a greater percentage lean body mass than do females so they almost always have higher basil metabolic rates your body temp have you ever heard that phrase feed a fever and starve a cold it's because your basil metabolic rate goes up in fever or whenever you have an increased temperature age there's a reduction of about 2% in your resting energy expenditure for every decade after 30 years so when you hear people say oh I just can't eat like I used to in my 20s it's because in your 40s and your 50s you're experiencing a 2% per year decline in your basil metabolic rate energy restriction we know that if you severely restrict your calories your basil metabolic rate will slow down it's a huge problem with people who yo-yo diet or have overly restrictive calorie diets you go down to 600 or 800 calories yeah you lose some weight right off the bat but your body immediately starts to think you're starving it and shuts down its basil metabolic rate because it doesn't want to be starved it needs to conserve energy genetics some people are just predisposition to having high or low basil metabolic rates your endocrine system plays a role your thyroid which controls your metabolism hypothyroidism is low thyroid it leads to a reduction or a sluggishness of your basil metabolic rate whereas hyper thyroid is when everything is revved up and your basil metabolic rate increases periods of growth have been shown to increase your basil metabolic rate okay so during pregnancy and breastfeeding um those things raise basil metabolic rate and stress raises your metabolic rate not just stress of like mental stress because you have a test coming up but any sort of stress related to your health condition you got in a motor vehicle accident or you have a big wound or a burn and your body's working to recover your basil metabolic rate will be higher than normal so that's your basal metabolism again that's about 50 to 70% of the energy you have spent physical activity is about 15 to 30% and it includes things like your plannned and daily activities walking doing yard work work rated activities fidgeting even fidgeting burns calories you might not have known that and then something called neat non-exercise activity thermogenesis this is the energy expended for everything that is not sleeping eating or sports like exercise okay so it's kind of like digesting and if you're fidgeting keeping your body warm that way this next slide has a lot of info on it but it's actually pretty straightforward if you take a second to look at it okay this is an equation called the Harris Benedict equation it's another way to help you determine calor needs I'll show you this way and then a much easier way next okay this is a validated equation that if you know somebody's height their weight and their gender as well as their activity level and whether or not they're sick you can calculate how many calories they need what their basil energy expenditure is remember from a couple slides ago that's basically how many calories do you need a day if you're a female that's the first bullet point your basil energy expenditure you take the number 6551 plus 9.6 * your weight in kilog plus 1.9 times your height in centimet minus 4.7 * your age in years if you want to calculate your weight from pounds to kilograms divide by 2.2 and if you want to calculate your height in centimeters multiply your height in inches times 2.54 so your weight in kgs is always less than your weight in pounds and your height in centimeters is always more than your height in inches think about that people usually want to weigh less than they do and be taller than they are so when you're converting from pounds and inches to kilograms and centimet you go down from pounds to kgs you go up from inches to centimeters for males the equation is 66.5 that's not a typo okay some people think oh it's supposed to be 665 it's not 66.5 plus 13.8 * weight in KS plus 5.0 * height in centim - 6.8 * H you can see that sub rating off the age component means that the older you get the less calories you get once you figure out your be in step two you multiply that times an activity factor and an injury Factor because being both sick and active Nets you more calories okay so you can look online to see what exactly determines a sedentary lifestyle versus low active versus active and very active but you would multiply your be times let's say you're a low active person 1.1 and if you're not sick you don't get an injury Factor if you are sick things like surgery can be 1 to 1.2 infections 1 to 1.4 um that's really something you learn kind of more in a clinical class okay but just keep in mind that being sick increases your injury needs or your calorie needs as well so if you have both an activity factor and an injury Factor you would multiply be times the activity Factor times injury factor and basically get how many calories you need a day or you can do it online there's a link to a calculator and it's a lot quicker another way to do your calorie needs if you're trying to figure out how many calories you need and you don't want to be bothered by that huge long equation you just saw is to do what's called the calories per kg method okay um this is a rule of thumb for determining how many calories a day you need and basically the way it goes is that if you want to maintain your weight multiply your weight in kgs by 25 to 30 if you want to gain weight you eat more so multiply your weight in kgs times 30 to 35 if you want to lose weight multiply your weight times 20 to 25 keeping in mind that 1 kilogram equals 2.2 lb okay so let's say we've got Barbie She's 5 fo 9 and she weighs 110 lb in the last lecture we talked about how to determine percent ideal body weight okay or what what ideal body weight is so let's start with what's Barbie's ideal body weight okay she's a 5'9 female using that hamway equation she gets 100 lb for being 5 foot and then you add 9 in * 5 lb per inch which is 45 so her ideal body weight would be 145 lb if we were asking for a range we'd usually give her plus or minus 10% but for the for the sake of this assignment let's just leave it and say Barbie's ideal weight is 145 but she only weighs 110 lb okay there all sorts of speculation if you were to actually make a real Barbie first of all she's anatomically impossible but they think she'd be 59 and 110 okay if she's supposed to weigh 145 and she only weighs 110 that means that she's only at 76% of her ideal body weight okay 110 ided 145 * 100 is 7 6 anytime someone is less than 85% of their ideal body weight we say that they need to gain weight okay so Barbie's only 76% of her weight she needs to gain weight okay so to gain weight we would multiply her weight in kgs times 30 to 35 okay so her weight in kgs is just 110 divided 2.2 which is 50 so I would do 50 * 30 which is 1500 and then 50 * 35 which is 8,750 if Barbie ate somewhere between 1,500 and 1750 calories it would help her gain somewhere between a half to 1 pound a week now to be honest most people are going to use this because they want to lose weight so You' multiply your weight in kgs times 20 to 25 and then you come up with two answers a lower end of the range and an upper end of the range A good rule of thumb is that on the days when you exercise you can eat the upper end of the range and on the days when you don't exercise aim for the lower end of the range how do you lose a pound of fat in a week this is a controversial approach to thinking about and I would argue it oversimplifies the relationship between calories and weight you can go online or really looking resources and there's some people who agree with this and some people who don't I just want to introduce it to you because you hear about it sometimes in the lay media there's some truth to it although it doesn't hold entirely true the notion is that a pound of fat contains approximately 3,500 calories of energy because the calorie is just a unit of heat energy right and there are seven days in a week so if you take the 3500 calories a day and divide it by seven days in a week an extra 500 calories a day you can cut that out so your Baseline minus 500 you can lose about a pound a week you now most of the fat diets that you read about or see about in the news or online they are based on the premise of calorie deficits they tell you hey you used to eat 3,000 calories now eat 2500 and guess what you're going to lose weight they might put together some magical approach or some special food that they say helps you lose the weight but the reality is you're running a calorie deficit and if you're overweight and can cut your calories down by 500 calories from your Baseline not 500 calories per day it's Baseline minus 500 every day okay you're going to lose about a pound a week now there's lots of other factors that go into weight loss of course you'll eventually get to the point where you can't lose any more weight and so on and so forth but this is a good premise for starting to think about how you might lose weight it's by cutting back on the calories in your food and of course by increasing the amount of exercise that you do