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If you’re trying to lose weight, you’re not alone. Almost half of American adults try to lose weight each year (Santos, 2017). With so many Americans setting weight loss goals every year, it’s unsurprising that the weight loss industry is booming. Pills, herbs, cleanses, detoxes, teas, fad diets, and more make unrealistic promises to lose weight fast. While these diet fads might be tempting, they’re not likely to produce the results they promise. So, how long does it take to lose weight?
How fast should you lose weight?
If you and your healthcare provider agree it’s safe and healthy to lose weight, most experts agree that a healthy weight loss program should aim to help you lose about 1–2 pounds per week (NIH, n.d.). How much total time it will take to reach your goals depends not only on the amount of weight you want to lose, but on several other factors like sex, age, medical status, medications, and more (Turer, 2015). To better understand how long your weight loss journey will take, let’s talk about how your body loses weight.
How does weight loss work?
The fundamental principle of weight loss is that to lose weight, you need to take in fewer calories than your body uses daily (also known as a calorie deficit). The same concept applies to weight gain in reverse—if you eat more calories than you burn, you will gain weight.
You might be familiar with calories from food. But many people are less familiar with how your body burns calories throughout the day. You can measure the calories you take in from food by knowing what’s in your meal, but it’s harder to predict how many calories your body uses each day. Factors like activity level, sex, and metabolism all impact how many calories your body burns, and at what speed.
Your body burns energy simply by being alive. Breathing, pumping your blood, and all the processes you don’t think about that keep your body running burn calories without you even trying. This process is called your resting or basal metabolic rate. Resting metabolic rate accounts for 60% of the total energy you use each day. The remaining energy fuels your physical activity and the digestion and absorption of your food (Popson, 2022).
Your resting metabolic rate stays relatively constant, but it can differ from person to person. Biological women tend to have a lower resting metabolic rate than biological men (Popson, 2022). Genetics may also have a role in determining resting metabolic rate, the tendency to gain weight, and obesity (Manini, 2011; Bahreynian, 2017).
Factors that affect weight loss
While your metabolic rate is an important predictor of weight loss, it’s not everything. Other factors have an impact on weight loss, including diet, exercise, age, and more (Anthanont, 2016).
There is no magic diet that guarantees permanent weight loss. It all comes down to the same fundamental principle identified above—you need to burn more calories than you eat. Your diet should include necessary nutrients and lower your calories while not being so restrictive that it’s impossible to stick to (Rynders, 2019). Some popular diet options include intermittent fasting, ketogenic diets, and the Mediterranean diet.
- Intermittent fasting. This diet means switching between eating and fasting, limiting eating to certain windows of time. Intermittent fasting may work for some pursuing weight loss because it helps to limit your calories (Rynders, 2019).
- Ketogenic diet. Also known as the “keto” diet, this eating plan encourages eating primarily fat, some protein, while limiting carbohydrate intake. This is one of several “low carb” diets. Keto diets may help with weight loss by forcing your body into ketosis, where you burn fat for energy instead of carbohydrates. Many have a hard time sticking to the keto diet because it’s so restrictive (Abbasi, 2018).
- Mediterranean diet. This diet is based on the eating habits of people living in Mediterranean countries. The diet limits red meat while encouraging fruits, vegetables, whole grains, seafood, lean meats, and monounsaturated fats like olive oil. Some studies suggest that the Mediterranean diet promotes weight loss more than “low fat” diets. However, other studies suggest weight loss on the Mediterranean diet is comparable to other similar diets (Mancini, 2016).
In addition to promoting general health, exercise promotes weight loss by increasing the number of calories that your body burns—you lose more weight with diet and exercise than just dieting alone (Johns, 2014).
Again, exercise is not just for weight loss. Exercise improves your overall health and wellness. Current physical activity guidelines recommend that the average adult perform 150-300 minutes of moderate exercise or cardio (like brisk walking) per week. Adding resistance training can also help increase lean muscle (HHS, 2018).
NEAT (or non-exercise activity thermogenesis) is another way to increase your activity. NEAT refers to the calories you burn doing simple movements like fidgeting, singing, cleaning, and other activities of daily living. You can burn up to an additional 350 calories per day with NEAT (Chung, 2018).
Some people find it harder to lose weight as they get older. However, we don’t know exactly why, especially since this experience can vary from person to person. Data suggests that metabolism and resting metabolic rate decline with age, which may play a role in weight loss becoming more difficult with age (McMurray, 2014; St-Onge, 2010).
Aging also tends to change body composition. People often lose muscle mass and increase body fat as time goes on (St-Onge, 2010). However, that doesn’t mean older adults are always less successful at losing weight. Other studies show that older people with a higher starting weight tend to lose more weight than younger people on the same diet. This could be because older people may be more motivated and stick to the long-term program (Finkler, 2012). Lastly, some research suggests that age does not play a role in keeping the weight off (Varkevissar, 2019).
As mentioned earlier, biological women’s resting metabolic rate tends to be lower than that of biological men (Popson, 2022). This partially explains why men often seem to lose weight faster than women. But, when it comes to weight loss, the answer is not that simple.
Biological women also have to deal with hormonal changes, like menstrual cycles, pregnancy, and menopause. Pregnancy can change fat distribution and increase how much fat builds up around the stomach. Menopause may trigger lasting weight gain due to the combination of aging and the loss of normal ovary hormone production (Perreault, 2019).
People with disrupted sleep are at higher risk for developing obesity or other weight-related issues (Medic, 2017). Lack of sleep may lead to excessive eating and difficulty losing weight. One study found that a lack of sleep increases your appetite, especially for calorie-rich, high-carbohydrate foods (Greer, 2013).
High levels of stress can wreak havoc on your body. Stress also seems to impact weight. Studies have shown that increased stress leads to weight gain and difficulty losing weight. Stress may also increase your cravings for high-calorie comfort foods (Sinha, 2018).
Certain medical conditions may cause weight gain and/or make weight loss harder and slower, including (Perreault, 2019):
- Thyroid problems
- Pituitary dysfunction
- Cushing syndrome
- Hormonal changes (PCOS, menopause, pregnancy)
Weight gain and difficulty losing weight is a common side effect for several types of medications, like corticosteroids, antipsychotics, and antidepressants, among others (Turer, 2015). If you suspect that any of these drugs are slowing your weight loss, talk to your medical provider about your options.
What happens if you lose weight too fast?
Experts recommend losing no more than 1–2 pounds per week, and for good reason. If you lose weight too fast, you run the risk of developing undesirable symptoms and serious medical problems, such as (Joshi, 2018):
- Menstrual changes
No matter what your weight loss journey looks like, you are more than your weight. No single body type is a reflection of health, and you can’t assess another person’s health simply by perceiving their weight. If you and your healthcare provider have agreed that weight loss is healthy for you, follow your treatment plan and treat your body with kindness. If you believe certain medications may be preventing you from achieving your weight loss goals, talk to your provider about alternative options.
If you have any medical questions or concerns, please talk to your healthcare provider. The articles on Health Guide are underpinned by peer-reviewed research and information drawn from medical societies and governmental agencies. However, they are not a substitute for professional medical advice, diagnosis, or treatment.
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Dr. Steve Silvestro is a board-certified pediatrician and Senior Manager, Medical Content & Education at Ro.