We are inundated from social media and other sources about diets and how well they work. In this post I’m going to describe the current most popular diets and how safe and effective they are at producing weight loss. I’m also going to write about the physiology of appetite, what controls appetite, and the mechanisms involved in weight regain after dieting. I will also discuss the ways people have discovered to maintain their weight loss. I am not going to discuss medicines for weight loss or bariatric surgery in this post. Those are subjects for another day. I did do a previous post on GLP1 agonists for weight loss. If you are interested you can link to that post here.

Energy Balance

Neither humans nor any other animal can survive without food. Our bodies convert food into the energy we need to keep our bodies intact and to be able to move about. The measure of the available energy in food is calories. A calorie is the amount of heat energy required to raise 1 gram of water by 1 degree centigrade. This is a very small amount of energy, so the unit we usually use is 1000 calories or kilocalories. When you see the number of calories on a food label, it is always means kilocalories even though it says “calories” on the label.

If on average we eat more calories than we use, our bodies store the extra energy as fat and we gain weight. If on average we use more energy than we get from our food, our bodies use the stored energy from fat and we lose weight. If on average we eat as many calories as we use, our weight is stable. We are in energy balance. We can also gain weight by increasing our muscle mass, but in this post I’m going to write about weight gain and loss as changes in body fat. This is an immutable law. Diet claims that calories don’t matter for weight loss are simply wrong. Calories in versus calories out sounds simple, but energy balance in our bodies is not simple at all.

Our intake of calories is controlled by our appetite and the control of appetite involves multiple hormones and neurotransmitters at multiple places in the brain and in the body. Control of appetite is very complex. I will write more about this later in this post.

Energy we use is of two types. A certain amount of energy is needed just to keep our bodies functioning. This is called the basal metabolic rate. It is also called resting energy expenditure (REE). It varies with weight. The average REE is 1 kilocalorie per hour per Kg (2.2 pounds) of body weight. That means that for a person who weighs 70 Kg (154 pounds) the REE would be 1680 kilocalories per 24 hours, just sitting on the couch. To calculate your own REE, divide your body weight in pounds by 2.2 and multiply that by 24. That will give you the number of calories you use in 24 hours just sitting on the couch during the day and sleeping at night. In general it is going to be in the neighborhood of 1500 to 2000 kilocalories per day.

The other type of energy we use is the energy required to move our bodies. These are called active calories. Active calories also based on body weight. For a 154 pound person, walking briskly burns 280 calories per hour. More vigorous activity burns more calories. Here is an extensive table from the Department of Health Services of Wisconsin that shows kilocalories burned for various activities at different body weights: CALORIES BURNED PER HOUR.

So what would it take for you to be in energy balance if you weigh 70 Kg (154 pounds) and do brisk walking for 30 minutes 5 days a week? Brisk walking uses 280 kilocalories per hour, so 140 kilocalories for each exercise session. That would be 700 kilocalories per week or an average of 100 kilocalories per day. Regular household activities burn about the same amount per hour as walking, so if you do household chores for 4 hours per day including weekends, that would be another 1,120 kilocalories per day. Your REE is 1680 kilocalories per day. You would be burning on average 100 active kilocalories per day for your walking and another 1,120 kilocalories a day for household chores for a total of 2900 kilocalories per day. That number will be a little higher if you weigh more that 154 pounds and a little less if you weigh less than 154 pounds. To be in energy balance you would need to eat no more than 2900 kilocalories per day. If you exercise more, you can eat more and stay in energy balance, but you would need to add a lot more exercise.

Fortunately, you don’t have to do all these calculations. In a normal weight person your body stays in energy balance automatically. Obviously, people who are overweight or obese either are not now, or at some point have not been in energy balance. It doesn’t take being out of energy balance much per day to cause significant weight gain. Lets suppose you take in 100 more calories per day than you use. It takes about 3500 extra kilocalories to gain a pound of fat. That would equal weight gain of fat at a rate of a pound every 35 days, or 10 pounds per year.

Being overweight or obese has serious health consequences that escalate with the degree of obesity. In order for overweight or obese people to avoid these consequences, they need to make a conscious effort to lose weight. That is where diets come in. Exercise is important too, but more for maintaining weight loss than losing weight. Of course exercise is good for you whether you lose weight or not.

Diets

I will write about the most extreme diets first, and then discuss the more moderate ones.

Keto (ketogenic) Diet

The brain is the second most active organ in the body after the liver. The brain normally uses glucose for energy but when glucose is not available and all the glycogen in the liver (which can be converted to glucose) is used up, the body starts to break down fat into something called ketones. The brain can use ketones for energy although it cannot use fat directly. The purpose of the ketogenic diet is to switch the whole body to the use of ketones for energy instead of glucose. This is accomplished by a high fat, very low carbohydrate and low protein diet. Protein has to be low because it can be broken down in the liver to form glucose. Carbohydrate is reduced to less than 50 grams per day which is less than the amount in a medium bagel. Protein is restricted to less than 1 gram per pound of body weight per day.

The ketogenic diet works because it decreases appetite, so despite eating calorie dense fat, total calories consumed are markedly decreased. It does lead to significant and fairly rapid weight loss. It is, however a markedly nutrient deficient diet. People who are on this diet must take supplemental multivitamins and minerals. Doing so keeps people from getting gross vitamin deficiency, but there is also a loss of micronutrients found in complex carbohydrates and it is unclear what the effects of this deficiency are. The ketogenic diet is very low in fiber, which alters the gut microbiome adversely. It decreases triglycerides and increases HDL, which are good, but it also increases LDL, which is bad. On the other hand, it decreases hypertension and has an anti-inflammatory effect. It is not clear whether the positive effects are outweighed by the LDL increase effects. So far, there is no evidence that ketogenic diets increase the risk of heart disease.

The main drawback of the ketogenic diet besides the nutritional deficiencies is that it is virtually impossible to stick to for more than a few weeks or months. Ketogenic diets do reduce insulin secretion since there is much less glucose for insulin to carry into the cells. The ketogenic diet may be useful in type 2 diabetics to reduce insulin resistance and decrease weight, particularly for diabetics in poor control. It is not a diet that can be maintained long term.

Very Low Calorie Diets

These diets restrict calories to 800 calories per day or less using proprietary liquid formulas that contain electrolytes and high protein to prevent muscle loss. VLCD diets lead to rapid and significant weight loss and are used primarily for people with severe obesity or medical complications of obesity. Such a diet should not be used without supervision of a physician. Again, like the ketogenic diet, VLCD diets should not be maintained long term.

Intermittent Fasting

Intermittent fasting is going without food for some period. Non-caloric drinks such as water or coffee are encouraged during fasting times. The simplest is restricted time eating. This involves skipping one or two meals per day and only eating during a restricted time. Whole day fasts can be once or twice a week or even every other day. One might think that a person would eat twice as many calories on a non-fasting day and so would not experience weight loss. This rarely happens. Intermittent fasting does reduce average calorie intake, and so people on any of the intermittent fasting regimens lose weight. People who start an intermittent fasting diet get very hungry at first on fasting days, but this hunger tends to decrease over time. It takes discipline to maintain intermittent fasting over a long period, but people who have the discipline to stick to the intermittent fasting regimen can stay on it long term. If the food they eat on non-fasting days is healthy (more on this later) then this can be a successful long term eating plan to maintain energy balance at a lower weight.

Paleo Diet

This is supposedly the type of diet that humans ate in the paleolithic period prior to agriculture when all humans were hunter gatherers. Of course people on the paleo diet do not become hunter gatherers. According to the Mayo Clinic a modern paleo diet includes fruits, vegetables, lean meats -especially game meats, fish, eggs, nuts and seeds. These are foods that in the past people could get by hunting and gathering. It doesn’t include foods that became more common when small-scale farming began about 10,000 years ago. These foods include grains, legumes and dairy products.

People on a version of the paleo diet do lose weight for exactly the same reason as weight loss on other diets. The average calorie intake on the paleo diet is substantially less than the standard American diet. It is not clear that excluding grains, legumes and dairy products is a good thing. Whole grains, legumes and dairy products supply high quality nutrients that may be missing in the paleo diet. The paleo diet is also more expensive and may be out of reach for lower income people. There are no long term studies of the health effects of the paleo diet.

Whole30 Diet

This is similar to the paleo diet but is recommended for 30 days. Foods to avoid are alcohol, sugar, dairy products and legumes and grains. There is a list of foods you can eat and all of these are unprocessed foods. The idea is that you reset your metabolism, and then you gradually add back the avoided foods and see how they make you feel. There is no evidence about the claimed long term good health effects of the Whole30 Diet. Like other diets that lead to fewer calories consumed, people do lose weight on this diet.

Plant based Diet

A plant based diet is exactly what it says. It is derived entirely from plants and eliminates all animal products including dairy products and eggs. The sources of protein are legumes, nuts, seeds, soy and lentils. Sources of fat are nuts, avocados, olive oil and vegetable oils. Plant based diets tend to focus on unprocessed foods. Unlike the other diets mentioned in this post, there is a lot of evidence that plant-based diets decrease the risk of developing diabetes (and also treat type 2 diabetes), decrease the risk of high blood pressure, heart disease and autoimmune diseases. Plant based diets have an anti-inflammatory effect, which probably is responsible for many of the benefits of plant based diets.

Unprocessed plant based food is more expensive than ultra processed foods and requires substantially more preparation time. People who live in poor neighborhoods often live in a “food desert” and unprocessed plant foods may not be available or be too expensive to buy. People who have low end jobs often have neither the time nor the equipment for food preparation. Although plant based diets have multiple health benefits, they are out of reach for a substantial part of the US population.

GOLO Diet

The GOLO diet is a proprietary diet plan you have to pay for. It is essentially a Mediterranean type diet that includes a supplement. The supplement has a lot of minerals and vitamins and there is no evidence that any supplement helps with weight loss. It is currently heavily advertised on television and social media. The research cited in all of these ads is research funded by the GOLO company. I will write about the benefits of the Mediterranean type diet next, but GOLO uses a standard dietary plan and a worthless supplement to make money. Don’t waste your money on this diet.

Mediterranean Diet

The original Mediterranean diet was the traditional diet of Crete, Greece and southern Italy in the 1960’s. Italians and Greeks no longer necessarily eat like this, but their original diet had lots of whole grains, vegetables and fish and used lots of olive oil. This type of diet has been studied more than any other and has very similar benefits to the plant-based diet. It reduces the risk of high blood pressure, diabetes, heart disease and autoimmune disorders. Here is the Mediterranean diet food pyramid from Wikipedia. It was developed by Oldways Trust, Harvard and the World Health Organization.

The things at the base of the pyramid are the things you eat the most and the things at the top of the pyramid you eat the least. Notice that red meat and butter are at the top of the pyramid. You don’t eliminate any class of food entirely in this diet, you just don’t eat the things at the top very often. Once again the diet includes mostly unprocessed foods and requires considerable food preparation.

The Standard American Diet (Also called the Western pattern diet)

Here is a description of the Standard American Diet from Wikipedia: The Western pattern diet is a modern dietary pattern that is generally characterized by high intakes of pre-packaged foods, refined grains, red meat, processed meat, high-sugar drinks, candy and sweets, fried foods, industrially produced animal products, butter and other high-fat dairy products, eggs,  potatoes, corn (and high-fructose corn syrup), and low intakes of fruits, vegetables, whole grains, pasture-raised animal products, fish, nuts, and seeds.

It is no wonder that we have an epidemic of obesity! The standard American diet is almost the exact opposite of the Mediterranean diet and plant-based diets. It is very high calorie and high in ultra-processed foods. That is why all of the diets I described above cause weight loss. Almost anything is better than the standard American diet!

Weight Regain After Weight Loss

With any diet (other than the very low calorie diets) weight loss stabilizes after a while and then there is very frequently some weight regain. Why does this happen? During the evolution of the human species, obesity was very rare. Hunter gatherers, even the few modern ones that remain in remote parts of the world are not fat. In evolutionary terms, weight loss meant that there was not enough to eat, so metabolic strategies to conserve calories during times of starvation had high survival value. The result is that when we lose a significant amount of weight, the body thinks we are starving. Several things happen to conserve energy. The first thing is that the basal metabolic rate or resting energy expenditure (REE) decreases an average of 50 kilocalories per day, but people who are obese to start with and lose a significant amount of weight can have decreases of REE as much as 700 kilocalories per day. Another body adaptation to weight loss is that the muscles become more efficient and use less fuel. This means that the calories you burn per hour with exercise decreases as you lose weight.

Appetite

As I mentioned before, the control of appetite is complex. Almost all control of appetite is unconscious. Appetite can be consciously controlled only for a short time, just as we can consciously control our breathing for a short time, but most breathing is (fortunately) unconscious. The part of the brain that controls our appetite and food intake is the hypothalamus. The hypothalamus secretes some hormones on its own and controls other hormones and/or peptides that both increase and decrease appetite. One hormone that increases appetite is Ghrelin. It is secreted by the stomach, small intestine, pancreas and brain and has multiple effects. It increases appetite and food intake and promotes fat storage. Hormones that makes you feel full or satiated are Leptin and GLP1. Control of appetite is actually a lot more complicated than this. Below is a table taken from a review article about hormonal control of appetite. Here is a link to the full article. It is not for the faint hearted. Hormonal Regulators of Appetite

The table summarizes what we know about the hormones and peptides that increase appetite and stimulate feeding and those that make us feel full and inhibit feeding. As you can see, control of hunger and satiety is very complicated. All of this takes place outside of our conscious awareness.

Hunger	Hormone	Primary location of production	Receptors	Action
Hypothalamus
	NPY	Medial arcuate nucleus (also widespread in CNS	Y1, Y5	Stimulating feeding and atagonizing satiety
	AgRP	Medial arcuate nucleus	MC3R and MC4R antagonist	Stimulating feeding
Peripheral Peptides
	Ghrelin	Stomach	GHS-R1a	Stimulating feeding by increasing NPY/AgRP and antagonizing Leptin effects
Satiety
Hypothalamus
	POMC/a–MSH	Arcuate nucleus	NC3R and MC4R	Inhibiting feeding, stimulating basal metabolic rate and altering nutrient partitioning
	CART	Arcuate nucleus		Inhibiting feeding
Peripheral peptides
	Cholecystokinin	Duodenum, jejunum	CCK-A	Inhibiting feeding and stimulating gall bladder contraction, intestinal motility, and inhibition of gastric motility
	PYY	Ileum, colon, rectum	Y2	Inhibiting feeding by inhibition of NPY and stimulation of POMC
	PP	Pancreas	Y4, Y5	Inhibiting feeding
	Oxyntomodulin	Distal ileum and colon	GLP-1 receptor	Inhibiting gastric acid secretion, decreasing gastric emptying and decreasing pancreatic enzyme secretion
	GLP-1	Distal ileum and colon	GLP-1 receptor	Delaying gastric emptying, stimulating glucose-dependent insulin secretion, inhibiting glucagon secretion and stimulating somatostatin secretion
	GIP	Stomach, duodenum, jejunum	GIP receptor	Glucose-dependent insulin secretion, induction of beta cell proliferation, promotion of energy storage, enhancement of bone formation
	Insulin	Pancreas	Insulin receptor	Inhibiting feeding
	Leptin	Fat cells	Leptin receptor, Ob-Rb	Inhibiting NPY and AgRP and stimulating POMC and CART
	Adiponectin	Fat cells	Adipo R1, R2	Inhibiting feeding

With significant weight loss (10% or more) the hormones that control appetite shift toward the hormones that make us hungry. Those includes Ghrelin, NPY and AGrP. The hormones that make us feel full, including leptin and others decrease.

The result of all this is that even if we are sure we are staying on the same foods, we are unconsciously eating more of them. The result is weight regain. The bad news is that 80% of people who lose weight on diets regain a substantial portion if not all of the weight they lost within 1-5 years. The good news is that 20% of people maintain most of the weight loss they achieved even after 5 years. How do those 20% of people who lost 10% or more of their body weight keep from regaining weight? We actually know a lot about how they do it.

National Weight Control Registry

Here is the introductory paragraph from the National Weight Control Registry website:

The National Weight Control Registry (NWCR), established in 1994 by
Rena Wing, Ph.D.  from Brown Medical School, and  James O. Hill, Ph.D.from the University of Colorado, is the largest prospective investigation of long-term successful weight loss maintenance. Given the prevailing belief that few individuals succeed at long-term weight loss, the NWCR was developed to identify and investigate the characteristics of individuals who have succeeded at long-term weight loss. The NWCR is tracking over 10,000 individuals who have lost significant amounts of weight and kept it off for long periods of time. Detailed questionnaires and annual follow-up surveys are used to examine the behavioral and psychological characteristics of weight maintainers, as well as the strategies they use to maintaining their weight losses.

The extensive research on the 10,000 people in the registry who have maintained weight loss show the following things that they do. This list is again from the registry website.

• 98% of Registry participants report that they modified their food intake in some way to lose weight.
• 94% increased their physical activity, with the most frequently reported form of activity being walking.
• There is variety in how NWCR members keep the weight off. Most report continuing to maintain a low calorie, low fat diet and doing high levels of activity.
• 78% eat breakfast every day.
• 75% weigh themselves at least once a week.
• 62% watch less than 10 hours of TV per week.
• 90% exercise, on average, about 1 hour per day. 

If you want to check out the registry for yourself, here is the link: The National Weight Control Registry

What all this research means is that it is possible to maintain weight loss despite the cascade of hormonal mechanisms that kick in to conserve calories when weight loss happens that work to get us back to the weight that we were. It is possible, but not easy. It takes continual effort, although people in the registry do report that it gets somewhat easier over time.

Bottom Line

1. All diets when adhered to result in weight loss
2. Some eating plans are sustainable and are not nutrient deficient. These include intermittent fasting, plant-based diets and the Mediterranean diet.
3. More extreme diets such as the Keto diet, VLCD diets and Paleo diet are not sustainable and have various nutrient deficiencies.
4. Substantial weight loss triggers hormonal changes in the body that conserve calories. These changes are responsible for the fact that weight loss plateaus on almost any diet and significant weight regain even often back to the original weight occurs in 80% of people who lose a substantial amount of weight.
5. It is possible to maintain weight loss over many years, but it is not easy. Findings from the National Weight Control Registry suggest the following strategies to maintain weight loss
   • Maintain a low fat low calorie diet
   • Exercise at least an hour a day
   • Weigh yourself at least once a week
   • Watch less than 10 hours of TV per week