Is Losing 100 Lbs. in a Year Healthy and Realistic?

I’ve lost 121 lbs. and kept it off for a long time. It took me about 8 years to lose the first 100 lbs., then another 9 years to maintain my weight loss and lose a little more. You, on the other hand, have set yourself the goal of losing 100 lbs. in a year. But is that a healthy and reasonable weight loss goal?

Most experts agree that losing 1-2 lbs. per week is safe. A year has 52 weeks. Therefore, it is healthy and realistic to lose up to 104 lbs. in a year. Losing more than 104 lbs. in a year, or losing the weight in less than a year, will require medical supervision. (265)

Just because it is healthy and realistic to lose 100 lbs. in a year does not mean it will be easy. There are unhealthy pitfalls and traps you will want to avoid along the way. Let’s dig deeper into what the next year of your life might look like. 

The Science and Math Behind Losing 100 Lbs. in a Year

To lose 100 lbs. in one year, you will need to lose, on average, 1.92 lbs. every week for 52 weeks in a row. Here is the math:

  • 100 lbs. divided by 52 weeks = 1.92 lbs. per week

1.92 lbs. per week falls within the recommended safe and maintainable weight loss targets of 1-2 lbs. per week.

Therefore, losing 100 lbs. in one year is safe and a reasonable goal to set for yourself without needing medical supervision!

For simplicity’s sake let’s round that number up to 2 lbs. per week for the entire year, and you could lose a total of 104 lbs. in a year while staying safe.

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How Many Calories Will You Need to Burn Each Day to Lose 100 lbs. in a Year?

One pound of fat is generally considered to be 3,500 calories.

This is a pretty good and simple point of reference for crunching the numbers on our journey. It is not perfect, and your scale will actually be a more accurate judge of your weight loss, but still… let’s stick with 3,500 calories per 1 pound of fat for simplicity’s sake.

Let’s say your goal is to lose 2 lbs. per week, on average.

2 lbs. = about a 7,000 calorie deficit per week

Since there are 7 days in a week, that means you will need to be in a negative calorie deficit of 1,000 calories per day.

If your daily maintenance caloric needs are 3,000 calories per day, you will need to consume 2,000 calories per day to safely lose 2 lbs. in a week, on average.

NOTE: Your daily caloric needs will change over time! Adjust your eating and physical activity as you progress in your weight loss journey.

Why Your Caloric Needs Will Change Over Time

The body burns calories essentially in 4 different ways:

  1. Basal Metabolic Rate (BMR) – The amount of calories your body needs to maintain all of its bodily functions.
  2. Thermic Effect of Food (TEF) – The amount of calories you burn digesting the food you eat.
  3. Non-Exercise Activity Thermogenesis (NEAT) – The amount of calories you burn while moving. This could be walking to work, doing the dishes, brushing your teeth, etc.
  4. Dedicated Exercise – The amount of calories you burn during dedicated exercise time. This could be going for a jog, swimming, time spent lifting at the gym, etc.

The percentage of calories burned each day varies a bit, but a reasonable estimate for each would be:

  • BMR – 70% of daily calories burned
  • TEF – 10% of daily calories burned
  • NEAT and Dedicated Exercise – 20% of calories burned

The first observation is that while physical exercise is important, it actually make up a surprisingly small percentage of how many calories you need in a day.  

The lesson here is that nutrition is the most powerful way to control your weight loss!

Exercise is very important, too, but you will not be able to lose 100 lbs. in a year with exercise alone. Your nutrition and hitting your weight loss caloric needs is critical for long term success.

And yet, your daily needs will change over time, too.

This can happen in the following ways:

  • Your BMR will decrease as you lose weight.
  • Your TEF will decrease as you eat less food.
  • Your NEAT will increase as you move more.
  • Your will need to eat more calories as you become more physically active.

This is why I recommend reassessing your caloric needs every month, and why I find the scale to be the most accurate and non-biased judge around. Much of this process will be guess-work, but the scale always tells the truth.

296 lbs. VS. 175 lbs.

10 Straightforward Steps to Lose 100 Lbs. in a Year

If you are serious about losing 100 lbs. this year, following these steps is a great place to start:

  1. Weight yourself right now, then come back.
  2. Measure your height right now, then come back.
  3. Think honestly about your current activity level. If you are not sure, do an Activity Audit for a week. Measure how often, how long, and how intensely you are physically active each day.
  4. Calculate your daily caloric needs using your current height, weight, and current activity level. You can use this Calorie Counter from to give you a solid baseline.
  5. Look at the “Extreme Weight Loss” box to get an estimate of what your daily caloric needs will be to lose 100 lbs. in this coming year.
  6. Eat these many calories every day.
  7. Increase your physical activity on a weekly basis.
  8. Weight yourself regularly and track your progress. I recommend weighing yourself every day or every week. What’s managed is what’s measured, so check in often.
  9. Make adjustments if the weight is not falling appropriately. Experiment and stay consistent.
  10. Repeat Steps 1-5 every month as your weight decreases and your activity level increases. You may find that your calorie needs also change over time.
My Calorie Counter Results: 34 years old, 85 kgs., 185 cm, pretty active

Easier said than done, I know! You will need to:

  • find food you enjoy eating long-term.
  • find exercises you enjoy doing consistently.
  • change your lifestyle.
  • overcome possible resistance and negativity from loved-ones, and yourself.
  • avoid temptations.
  • recover quickly from relapses.
  • do this consistently.

I’m not saying it will be easy. It wasn’t for me. But in its simplest form, this is how it is done.

Is Losing a Lot of Weight at the Beginning Bad for Your Health?

As you begin your 100 lb. weight loss journey, you may find that the weight initially falls off quickly. It did for me, and it can be a very motivating and encouraging start.

This happens for two main reasons:

  1. High Initial Basal Metabolic Rate – When you are at your heaviest, your maintenance calories to maintain your heavy weight are very high. For example, you may start with a daily maintenance calorie level of 4,000 calories just to maintain your current weight. It is easier to create a calorie deficit during this period. As you lose weight, this number will drop, meaning your weight loss will become less dramatic and will require more work.  
  2. Water Weight – As you start losing weight, your body will begin using stored energy. This energy is called glycogen. Glycogen is bound to your body by water. As you burn up your glycogen stores, you will also break the water bonds holding them together. It can result in rapid initial weight loss. The effect of this diminishes over time.

Note that losing a lot of weight fast can be dangerous for your health. Rapid weight loss is defined as:

Rapid Weight Loss = losing more than 2 lbs. per week

According to Healthline, rapid weight loss can cause the following:

  • muscle loss
  • gallstones
  • nutritional deficiencies
  • drop in metabolism

This type of weight loss is normally associated with crash dieting and other unhealthy practices such as starving yourself, binging and purging, taking diet pills, etc.

Not only is this incredibly unhealthy, it is also not sustainable in the long term, making regaining the lost weight inevitable.

Will Your Weight Loss Be Consistent Every Week?

Expectation Vs. Reality of a 100 Lb. Weight Loss

Your weight loss will not be consistent every week.

Weight loss is not linear. You will notice that some weeks you lose more weight and some weeks you lose less weight. This has to do with many factors, some of which include:

  • emotional stress
  • mental stress
  • muscle gain
  • changes in bone density
  • water retention due to types of food eaten (carbs and sodium can retain more water)
  • accuracy of your scale
  • consistency in weighing yourself at the same time and under the same conditions for each weigh-in (natural fluctuation of weight during the day based on food and beverages consumed)

Instead of fretting about small changes in the short term, look to see that your weight is continuing to fall over the long term.

If you go too long, however, in a plateau without any additional weight loss, it will be time to honestly reassess how much you are eating and your daily physical activity.

We have a tendency to underestimate how much we eat and overestimate how physically active we are. Plateaus are most often the result of eating more calories than you think you are and/or working out less than you think you are. BE HONEST with yourself if you come to this point.

Will You Have Loose Skin After Losing 100 Lbs.?

You can see my loose skin after a 121 lbs. weight loss in this picture!

Having loose skin after an extreme weight loss of 100 lbs. is normal, but not inevitable. So, yes, it is very likely that you will have some loose skin, but it is not a guarantee, either.

The excess fat in your body caused your skin to stretch. Your body will shrink as you lose the 100 lbs., but the excess skin will probably not return to its original shape and form after stretching so much.

When you also consider that skin elasticity (due to collagen and elastin in your body) decreases with age, it means that it might be even tougher to tighten up and tone up than in your younger days.

The amount of excess skin that you have varies from person to person.

Some people may end up with a lot, while others may experience very little loose skin. Consider some of these factors as you progress in your weight loss journey:

  • Losing the weight slowly and gradually gives your skin more time to adjust and tighten up. Faster weight loss can lead to more loose skin.
  • Proper nutrition feeds your body and allows it to recover. Your skin is composed of what you eat, right?!
  • Exercise can build and tone your muscles. A stronger frame will “fill-in” some of that loose skin.
  • Do you smoke cigarettes? Cigarettes lowers skin elasticity and may lead to more loose skin?
  • How about sun exposure? Sun damage also reduces skin elasticity and could lead to more loose skin.
  • Genetics – not much we can do about this, other than to do your best!

I have a little bit of loose skin myself despite losing my first 100 lbs. over the course of 8 years, give or take. It was something I was actually worried about in my weight loss journey.

Still, I am much happier (and healthier!) in the skin that I am currently in then when I weighed 296 lbs. I know that you will be, too!

What Does Losing 100 Lbs. Do for Your Health?

According to the Centers for Disease Control (CDC), obese people are at an increased risk for the following:

  • Premature death
  • High Blood Pressure
  • High Cholesterol
  • Type 2 Diabetes
  • Coronary Heart Disease
  • Stroke
  • Gallbladder Disease
  • Osteoarthritis
  • Sleep Apnea and Breathing Problems
  • Many Types of Cancer
  • Low Quality of Life
  • Mental Illness such as Clinical Depression, Anxiety, and Other Mental Disorders
  • Body Pain and Difficulty with Physical Functioning

That is quite the list!

The good news is that you do not necessarily need to lose 100 lbs. to get make improvements in these health areas. Even a 5-10% reduction in your weight can make a huge difference in your overall health and quality of life.

Of course, losing 100 lbs. in a safe, long-term, maintainable way will amplify these health benefits for you. They did for me!

My Personal 121 Lbs. Weight Loss Story

When I was 17 years old, I weighed 296 lbs.! I was Class II Obese, and I was not even a legal adult yet.

Fortunately for me, I realized young enough that I was heading down a dangerous road. I started to change my lifestyle and began living a healthier, more active, life.

It took me about 8 years to lose 100 lbs. for the first time, and it felt great! I was exercising regularly, hiking often, cooking and enjoying healthier foods, and the quality of my life was the best it had ever been.

In the 9 years since then I have mostly maintained my weight loss, albeit with a few short relapses along the way. Now, 17 years later, I am happy to say that I have lost a total of 121 lbs. and that I have continued to maintain this weight loss in the long term.

I credit lifestyle change, patience, determination, and developing healthier habits with my ability not only to lose the weight, but also to maintain the weight lose for such a long time.

I am also thrilled to let you know that I recently became a Certified Personal Trainer, Certified Nutrition Coach, and a Certified Weight-Loss Specialist through the National Academy of Sports Medicine (NASM) organization. I’m dedicated to continuing to live a healthy lifestyle for myself, and in helping you to do the same!

Check out the Article and YouTube Video!

I wrote a full article detailing my journey called How I Lost Over 100 Lbs. and Kept It Off for Years! Click the link to give it a read and to learn more about my personal journey, complete with before-and-after photos!

More directly, I sincerely wish you all the very best as you continue your personal weight loss journey. It will not always be easy, but the best things in life rarely are.

I know you can do it, and I hope this article was helpful in taking the first step.

Let’s continue to become the people we wish to be and to support each other along the way. Together, we can make a healthier world with a higher quality of life for all.



Jack Clancy

Everything I do is focused on this concept: "To inspire personal change, so that together we can become the people we wish to be."

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