Dieting and Weight Regain: Basal Metabolic Rate, Appetite Hormones, and Sustainable Weight Loss

There are all sorts of dieting methods, from eating only apples and bananas to hard-boiled eggs, intermittent fasting, and even the ketogenic diet. Initially, they often show results: it's not uncommon to lose two or three kilograms within a week or two. However, many people find that their weight stops decreasing after a while, and once they return to their original diet, their weight rebounds more quickly, sometimes even exceeding their pre-diet weight.

This phenomenon is not due to a lack of willpower. Research over the past two decades shows that...There is a clear physiological basis for the weight regain.Dieting alters the hormones that regulate appetite and reduces the body's energy expenditure (metabolic adaptation), both of which contribute to weight regain. Understanding these two factors is crucial to finding truly sustainable practices.

The good news is that maintaining weight in the long term...Not out of reachThis article will use verifiable research to explain why the weight returned and what people who successfully maintained their weight actually did right.

I. Dieting for weight loss: Why is it effective initially but easy to regain the weight in the long run?

Regardless of the dieting method used, the principle is the same.Reduce calorie intakeWhen you consume less than you burn, your body will use stored energy, leading to weight loss. The initial effects are usually noticeable, which explains why dieting is always so appealing.

The problem arises in the next stage. When weight drops to a certain level, even...Even with strict dietary control, my weight stopped decreasing.This can lead to what's known as the "hitting the wall" phase. During this time, feelings of frustration are common, causing people to give up dieting, revert to their original eating habits, and consequently gain weight rapidly.

It should be noted that,Weight gain often happens faster than weight loss.This isn't because dieting "damaged the body," but rather because the body initiates a series of adjustments when energy is insufficient: appetite increases and energy expenditure decreases. The next two sections will explain these two mechanisms separately.

2. If you lose weight quickly, is it fat or water that you're losing?

In the initial stages of dieting, weight loss often occurs faster than in the later stages. This portion is indeed fat, but...A significant proportion comes from changes in body water and glycogen.。

The body uses excess sugarGlycogenGlycogen is stored in the liver and muscles. It is stored with water – approximately 1 gram of glycogen contains water. 3 grams waterWhen carbohydrate intake is drastically reduced, glycogen is broken down to provide energy, and this water is also excreted in urine, resulting in a significant weight loss in a short period of time (source at the end of the article). The Victorian government's health education agency in Australia also pointed out that the weight loss in the initial stage of a low-carbohydrate diet is "mostly water, not body fat."

Table 1: Components of Weight Loss (Initial Diet vs. Continued Diet)

stage	Weight loss mainly comes from	Features
Initial phase (first few weeks)	Glycogen along with its accompanying water and some fat	The rapid decline can easily lead people to believe that they have successfully lost weight.
Duration (several weeks later)	Mainly fat	The slower descent speed is normal.
After resuming normal diet	Hydration and glycogen replenishment	Weight rebounded rapidly, especially due to water retention.

This also illustrates one thing:The number on the pound does not directly equate to the increase or decrease in body fat.To truly assess effectiveness, in addition to weight, it's also important to consider waist circumference and overall body condition. For further information on why waist circumference is a better indicator of metabolic risk than weight, and measurement methods, please refer to [link to relevant article].How to measure weight loss results? Waist circumference is a better indicator of metabolic risk than weight.〉。

III. Appetite Hormones: The Physiological Driving Force Behind Weight Gain

The most compelling explanation for the weight regain comes from a study published in the New England Journal of Medicine (Sumithran et al., 2011).PubMed 22029981Research Invitation 50 overweight or obese adults without diabetesto carry out for a period of time 10 weeksA very low-calorie diet plan was implemented, followed by a personalized weight maintenance plan. The result was:

• Average subtraction during the planning period 13.5 kg；
• Follow-up was conducted one year later (week 62 of the study).The average increase is about 5 kg.；
• The study simultaneously measured multiple hormones that regulate appetite and found...A year later, I still haven't returned to my pre-weight loss level.。

Specifically, these are signals that reduce appetite and create a feeling of fullness (leptin, peptide YY, cholecystokinin, insulin, amylin).persistently lowMeanwhile, appetite-stimulating signals (ghrelin, gastric inhibitory peptides, pancreatic peptides)persistently highThe subjects' subjective feelings of hunger remained higher one year later than before they lost weight.

The research team's conclusion was quite straightforward:The signals that lead to weight regain after weight loss can last for at least a year.Therefore, a long-term strategy is needed to address this, rather than just a one-time diet. Another study also observed that these appetite-related hormonal changes are not significantly related to age, gender, or weight loss methods; they are simply a general bodily response to weight loss.

In other words, feeling persistently hungry and craving food after dietingIt's the body "exerting force" to pull its weight back to its original level.This is a normal physiological phenomenon, and readers should not blame themselves for it.

IV. Metabolic adaptation and basal metabolic rate

Basal metabolic rate(Or resting metabolic rate) refers to the minimum amount of energy required for the body to maintain heartbeat, respiration, body temperature, and organ function at rest. It is not a small amount: the National Academy of Sciences' Dietary Reference Intakes for Energy state that...Resting energy expenditure typically accounts for 601 TP4T to 701 TP4T of total daily energy expenditure.（National AcademiesThe remainder comes largely from the thermic effect of food (about 10%) and physical activity.

When a person continuously loses weight on a low-calorie diet, the body will conserve energy by...Actual energy expenditure was lower than the expected value calculated based on body weight.This phenomenon is calledMetabolic adaptationThis is also known as adaptive thermonuclearization. This means that the same amount of food is more likely to produce a calorie surplus when metabolism slows down.

How long can metabolic adaptation last? A long-term follow-up study of contestants in "The Biggest Loser" provides some clues (Fothergill et al., 2016;PubMed 27136388The study focused on pre-competition, post-competition (30 weeks) and post-competition (30 weeks) activities. Six years laterThe weight, body composition, and resting metabolic rate of the 14 participants were measured respectively:

• During the competition, the average subtraction of approximately 58.3 kgThe resting metabolic rate decreases by approximately 610 kcal/day；
• Average after 6 yearsThe weight increased by approximately 41 kilograms.；
• Six years later, the resting metabolic rate was still higher thanBefore weight loss, my daily intake was as low as 704 kcal/day.Metabolic adaptation is approximately -499 kcal/dayThat is, it is about 500 kcal lower than the expected value calculated based on the weight at that time.

The research team concluded that:Metabolic adaptation continues over timeThis is the body's response to weight loss. Looking at these two studies together, the reason for weight regain becomes clear:On the one hand, appetite increases, and on the other hand, energy expenditure decreases; these two forces simultaneously push weight upward.This is not a case of physical "breakdown," but rather that the body's original mechanisms for coping with food shortages have become obstacles in the modern environment of food abundance.

It is worth emphasizing that the extent of metabolic adaptation varies from person to person, andPeople who maintain a higher muscle mass and a sufficient level of physical activity usually have an advantage.This is why "diet plus exercise" is more worthwhile than "diet alone"—see Sections 6 and 8 for details.

5. Is it true that "90% of people regain weight"? What are the actual long-term maintenance data?

The claim that "90% of dieters eventually regain the weight" is widely circulated, partly stemming from older literature. Recent meta-analyses have provided a more accurate and promising picture.

A covering 29 studiesA comprehensive analysis examined the long-term outcomes of those who completed structured weight loss programs (Anderson et al., 2001).PubMed 11684524The conclusion is:Five years after the plan was completed, the average weight loss was still more than 3 kilograms, equivalent to more than 31 TP4T of the initial weight.Among them, those who adopted a very low-calorie diet maintained significantly better results (maintaining approximately...). 29% (For weight loss), those who maintain a typical low-calorie balanced diet will maintain approximately [weight loss percentage]. 17%。

In other words, on averageNot all of them will return.However, a significant portion will indeed rebound—this cannot be ignored. The same analysis also yielded another useful finding for the reader:The group with higher levels of physical activity maintained significantly better weight than the group with lower levels of physical activity.。

So where does the "90%" figure come from? A more reasonable understanding is:Returning to or exceeding one's original weight is indeed common, but it's not the only outcome.Moreover, whether it can be maintained depends closely on the methods (especially the ability to maintain dietary and exercise habits in the long term), and is not predetermined.

6. What did people who successfully maintain their weight do right?

This is perhaps the section most worth reading carefully in this article.

A widely cited review points out that,Overweight individuals with approximately 20% can successfully maintain their weight long-term.(defined as losing at least 101 TP4T of initial weight and maintaining that weight for at least one year) (Wing & Phelan, 2005;PubMed 16002825The study also cited data from the National Weight Control Registry (NWCR): Registrants lost an average of approximately [missing information - likely weight loss percentage]. 33 kgand maintain more than 5 years。

More importantly, successful people are not necessarily gifted, but rather...Did a few things right：

Table 2: Common Practices of People Who Successfully Maintained Their Weight

practice	Specific content
Maintain a high level of physical activity	Registered members spend an average of about 1 hour active per day, with walking being the most common activity.
Maintain a low-calorie, low-fat diet	It doesn't mean reverting to your original diet, but rather maintaining a relatively light diet long-term.
Eat breakfast regularly	Most members eat breakfast every day.
Regularly measure your weight	Using weight as a tool for "early detection," not for judgment.
Weekday and weekend diets are the same	Avoid letting weekend indulgence negate weekday efforts

The study also made an encouraging discovery:Weight maintenance may become easier over time.After successfully maintaining this for 2 to 5 years, the chances of achieving long-term success increase significantly. This means that the most difficult part is the first half, but things become easier once you get past that.

Therefore, rather than viewing dieting as a "short-term sprint," it's better to understand it as...Establish a diet and activity pattern that can be maintained long-term.This also aligns with the direction of this article and the original manuscript: dieting alone has limited effectiveness; a balanced diet combined with regular exercise is the sustainable path.

7. How to lose weight sustainably? Safe speed, calories, and nutrition.

Since weight regain is related to "excessive restriction," a feasible approach is...Keep the restrictions within the limits that the body can tolerate.。

Table 3: Basic Principles of Sustainable Weight Loss

project	suggestion
Weight loss speed	About once a week 0.5 to 1 kgRelatively safe and more likely to be maintained
Calorie deficit	Approximately more than the daily requirement for maintaining body weight600 kcal less
Very low calorie diet	Daily below 800 kcaldietIt must be carried out under medical supervision.
Dietary contents	Consume mainly fruits, vegetables, whole grains, high-quality protein, and low-fat dairy products; reduce consumption of high-sugar, high-fat, and sugary drinks.
Dietary patterns	Adjust gradually, allowing your body to adapt to the new intake, rather than suddenly reducing it drastically.

The UK's National Health Service (NHS) recommends that to achieve a weight loss rate of 0.5 to 1 kg per week, one generally needs to consume about 600 kcal less per day than the body requires, and reminds [the public] of this.It is not advisable to reduce calorie intake too much without medical supervision.Otherwise, they may not be able to get enough nutrients. Very low calorie diets (less than 800 kcal per day) should only be considered under medical supervision and in specific circumstances.

"Gradual adjustment" is key. Compared to drastically reducing food intake all at once,Small, sustainable changesIt allows the body to adapt more easily and is less likely to cause a rebound after a few weeks. For more information on the practical methods and benefits of a balanced diet, please read <<>.6 major benefits of a balanced diet〉。

In Hong Kong, the Department of Health, in its "Weight Management Action Plan," proposed a three-stage approach to promote weight management: "raising awareness, proactive change, and integration into daily life," and emphasized...Maintaining a balance between calorie intake and expenditureReduce high-fat and high-sugar foods, eat more vegetables, fruits, and whole grains, choose lean meats and low-fat dairy products, use low-fat cooking methods, and limit high-fat sauces and sugary drinks.Hong Kong Special Administrative Region Government Press ReleaseThe Elderly Health Centre of the Department of Health also reminds the public that...You should eat at least 5 servings of fruits and vegetables every day.Choose more whole grains to increase dietary fiber and satiety.Department of Health Elderly Health Centre）。

Regarding the claim that "you can lose weight by only drinking a certain beverage," it's worth paying attention to the sugar content and portion size. Further discussion can be found in the following article:The Nutritional Truth About ABC Fruit and Vegetable Juices>and<Sugar and fructose metabolism in fruits〉。

8. Exercise: The key to maintaining weight and preventing weight regain.

If dietary control is responsible for "weight loss," then exercise plays a more prominent role in "maintenance." The meta-analysis cited earlier has already pointed out that...The group with higher exercise levels maintained significantly better weight.Among the common practices of those who successfully maintain their weight, regular exercise is the most consistent one.

Regarding exercise, the World Health Organization recommends (compiled by the Department of Health's "Living a Healthy New Direction") that adults aged 18 to 64 should...Engage in at least 150 to 300 minutes of moderate-intensity aerobic physical activity each week.Or 75 to 150 minutes of vigorous activity, or a combination of both; andEngage in muscle-strengthening activities targeting major muscle groups at least two days a week.,at the same timeReduce sitting time（Department of Health's "Living a Healthy New Direction"）。

Why include muscle-strengthening activities? Because maintaining and increasing muscle mass helps preserve metabolic capacity during weight loss, combating the metabolic adaptations mentioned earlier. Aerobic and anaerobic (resistance) exercise each have their roles; combining them is more comprehensive than doing either one alone—see details below.The differences and benefits of aerobic and anaerobic exercise〉。

In practice, exercise routines can be varied, such as alternating between running, cycling, skipping rope, or ball sports each week, which makes it easier to maintain interest and motivation. Warming up and stretching before and after exercise also helps reduce the risk of injury. Importantly...Make it a part of your lifeIt is not a temporary task during dieting.

IX. Safety and Medical Advice

Weight management deserves serious attention because weight is closely related to metabolic health. For Asian adults as a reference: a Body Mass Index (BMI) of 23 to under 25 is considered overweight, and 25 or above is considered obese; a waist circumference of 90 cm or more for men and 80 cm or more for women is considered central obesity.Department of Health Elderly Health CentreThe World Health Organization also points out that being overweight and obese increases the risk of many non-communicable diseases.WHO）。

In the following situations, it is advisable to consult a doctor or registered dietitian first, and not to attempt extreme dieting on your own:

• The plan is to significantly reduce calorie intake to below 800 kcal per day.Or engage in prolonged fasting;
• Suffering from chronic diseases such as diabetes, heart disease, and kidney diseaseOr are currently taking long-term medication;
• During pregnancy or breastfeedingas well asUnder 18 years oldPeople;
• Unexplained and continuous weight lossExperiencing binge eating or vomiting after eating, or being significantly distressed by weight problems.

In addition, if weight gain is accompanied by fatigue, cold intolerance, edema, or other symptoms, it is advisable to consult a doctor to check for other underlying causes. A healthy weight loss goal is...Long-lasting changesRather than the largest drop in a short period of time.

10. Frequently Asked Questions

Will I definitely gain the weight back after dieting?

No. Weight regain is indeed common, but not inevitable. Studies show that about 20% of overweight individuals successfully maintain their weight long-term (minus at least 101 TP4T of initial weight and maintaining it for at least one year), and the chances of long-term success increase significantly after maintaining it for more than two to five years. The key is whether the method can be implemented in the long term.

Why do you lose weight so quickly in the early stages of dieting?

Because a significant portion of the initial weight loss comes from body water and glycogen. When glycogen is stored, approximately 1 gram is accompanied by 3 grams of water. As carbohydrate intake decreases and glycogen is broken down, this water is excreted along with the glycogen. Therefore, rapid weight loss in the initial stages does not necessarily equate to fat loss.

Can a decreased basal metabolic rate be reversed?

Metabolic adaptation during weight loss is a normal bodily regulation process that continues for a period of time. Studies show that people who maintain more muscle mass and sufficient activity levels generally have an advantage. Therefore, it is not recommended to rely solely on dieting; it is advisable to combine it with adequate protein intake and regular exercise.

Is it true that "90% of people who lose weight regain it"?

This claim is partly based on older literature. More recent meta-analyses show that those who complete a structured weight loss program maintain an average weight loss of over 3 kg five years later, and not all regain it. However, weight regain is indeed common; the key is to mitigate the rate of regain in a sustainable manner.

Can fasting or very low-calorie diets be used?

Extremely low-calorie diets (less than 800 kcal per day) should only be undertaken under medical supervision and in specific circumstances, as they may lead to risks such as nutritional deficiencies. If you plan to adopt a prolonged fasting or extremely low-calorie diet, please consult a doctor or registered dietitian first.

How many kilograms can you safely lose in a week?

It is generally recommended to lose about 0.5 to 1 kilogram per week, which is equivalent to about 600 kcal less than the body's daily requirement. This rate is safer and more likely to be maintained in the long term; a faster decline at the beginning is common, but it will slow down afterward, which is a normal process.

Will I gain weight back after following a ketogenic diet?

The ketogenic diet reduces total calories through a combination of very low carbohydrates and high fats, often resulting in significant initial weight loss. However, a large portion of this weight loss comes from changes in glycogen and water retention. Weight is easily regained when resuming a normal diet; long-term effects are not significantly different from other sustainable diets. It is advisable to consult a professional before starting this diet and ensure adequate nutrient intake. Further reading on this topic can be found in the article "Nutritional Deficiencies of the Ketogenic Diet" on this website.

Can you lose weight by exercising alone?

Weight loss through exercise alone is usually less effective than diet control, but...Maintaining weight and preventing weight regainIn this regard, exercise plays a very prominent role. The ideal approach is to combine diet and exercise: create a moderate calorie deficit through diet and maintain muscle mass and activity level through exercise.

How much weight gain should you be concerned about?

Weight can fluctuate by 1 to 2 kilograms daily due to factors such as water retention, salt levels, and the menstrual cycle. A single reading should not be over-interpreted. It is more practical to observe the trend over a period of time (e.g., 2 to 3 weeks). If the trend continues to rise, diet and activity can be adjusted early, rather than waiting for a significant rebound before taking action.

When should you see a doctor or nutritionist?

If you plan to drastically restrict calories, have a chronic illness or are taking long-term medications, are pregnant or breastfeeding, are under 18 years old, or are experiencing unexplained and persistent weight loss, binge eating, or purging, you should consult a professional first. Personalized advice is safer and easier to implement than a generic plan.

XI. Sources of Information

• Sumithran P, et al. Long-term persistence of hormonal adaptations to weight loss. N Engl J Med. 2011;365(17):1597-1604. PubMed 22029981
• Fothergill E, et al. Persistent metabolic adaptation 6 years after “The Biggest Loser” competition. Obesity (Silver Spring). 2016;24(8):1612-1619. PubMed 27136388
• Anderson JW, et al. Long-term weight-loss maintenance: a meta-analysis of US studies. Am J Clin Nutr. 2001;74(5):579-584. PubMed 11684524
• Wing RR, Phelan S. Long-term weight loss maintenance. Am J Clin Nutr. 2005;82(1 Suppl):222S-225S. PubMed 16002825
• National Academies of Sciences, Engineering, and Medicine:Dietary Reference Intakes for Energy (Percentage of Energy Consumption Based on Metabolism and Resting Energy)
• Department of Health's "Living a Healthy New Direction":Physical activity guidelines for adults (18 to 64 years old)
• Hong Kong Special Administrative Region Government Press Release:Legislative Council Question 19: Raising Public Awareness of Weight Management
• Department of Health Elderly Health Centre:Weight Management
• World Health Organization:Obesity and overweight；Healthy diet
• NHS:Healthy weight；Better Health: Lose Weight
• National Institute of Diabetes and Digestive and Kidney Diseases:Weight Management
• Better Health Channel (Victorian Department of Health):Weight loss – common myths

Extended reading within the site

• How to measure weight loss results? Waist circumference is a better indicator of metabolic risk than weight.
• The differences and benefits of aerobic and anaerobic exercise
• 6 major benefits of a balanced diet
• The nutritional truth about ABC fruit and vegetable juices: What do you get in a glass of apple, beetroot, and carrot juice?
• Sugar and fructose metabolism in fruits: Can fruits replace vegetables or regular meals?
• Causes of constipation, dietary care, and timing of seeking medical attention
• Causes and symptoms of edema: When to seek medical attention for facial or leg swelling.
• Ketogenic diet lacks nutrients

Health Disclaimer:This article provides general health and nutrition information and should not replace a doctor's diagnosis, treatment, or personalized advice. Any dietary or weight adjustments, especially for pregnant women, breastfeeding women, individuals under 18 years of age, those with chronic illnesses, or those taking medications, should be discussed with a doctor or registered dietitian first. If you experience unexplained and persistent weight loss, signs of eating disorders, or persistent discomfort, please seek medical attention as soon as possible.

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