How Many Calories Are in a Pound of Fat?

Parents often wonder how their kids can gain so much weight so quickly, especially when their diets aren't that terrible. After all, your kids don't need to be eating a big bag of chips, a double serving at each meal, a mega-sized soda, or a bedtime snack every night to become overweight.

Although that would usually do it, more often it is smaller things that creep up on you and it's a few extra calories that add up day after day that causes kids to become more and more overweight.

A person holding milk with a nutritional label

Oscar Wong / Getty Images

Calories and Fat

Understanding how many calories it takes to gain a pound of fat can help you understand how this happens. That's why a medical doctor in 1958, Max Wishnofskly, created an equation rule to figure out that one pound of fat is equal to about 3500 calories. That means that if you eat an extra 350 calories of food a day, which is about equal to a large piece of cake or a medium milkshake, you would gain an extra pound about every 10 days (350x10). Or you would gain a pound in about 20 days if you eat or drank an extra 175 calories a day (175x20).

On the other hand, eating 175 fewer calories a day could mean that your kids could lose a pound every 20 days.

Or if they kept their diet the same, but burned an extra 175 calories a day by exercising more, then again, they could lose a pound in about 20 days.

How can this help you if your kids are gaining a lot of weight?

If you calculate how quickly they are gaining weight, it can help you to figure out how much they may be overeating. If your child is gaining a pound every 10 days, for example, then they are likely overeating by about 350 calories a day.

New Weight Loss Math

Of course, it is a lot more complicated than that, since that doesn't factor in how much or how little they are exercising or the fact that younger kids should normally be gaining some weight, so talk to your pediatrician or a registered dietician before adjusting your child's diet based on this kind of calculation.

This idea also doesn't take into account that our bodies often adjust their metabolism to try and keep you at the same body weight. So if you are very overweight and lose a lot of weight, your metabolism will likely slow to push you to gain weight again, even if you are eating fewer calories. This is one of the reasons why it is so hard to lose weight and keep it off.

It is also a very good reason why you should help your kids develop healthy habits at a young age so that they don't become overweight in the first place.

The 3,500-Calorie Rule can still be a good basic way to think about weight gain and loss, though, as long as you understand its limitations.

Losing Weight With Small Steps

If your child is overweight, he almost certainly needs to lose more than a pound, but you will likely be more successful starting with small steps instead of looking for quick weight loss with drastic changes.

Can you find little things in your child's diet that you could change?

How about changing to a lower fat milk? Just going from whole milk to 1 percent milk, if your kids drink 3 cups a day, will save about 150 calories a day, which could translate into a pound every 20 days.

Or if you get your kids to stop drinking soda each day, that 12-ounce can of soda will save you 155 calories a day, or a pound in about 23 days.

These small changes, although they may not seem like much, will add up quickly and help your kids lose weight, just as easily as they helped them to pile the pounds on.

3 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Thomas DM, Gonzalez MC, Pereira AZ, Redman LM, Heymsfield SB. Time to correctly predict the amount of weight loss with dieting. J Acad Nutr Diet. 2014;114(6):857-861. doi: 10.1016/j.jand.2014.02.003

  2. Johannsen DL, Knuth ND, Huizenga R, Rood JC, Ravussin E, Hall KD. Metabolic slowing with massive weight loss despite preservation of fat-free mass. J Clin Endocrinol Metab. 2012;97(7):2489-2496. doi: 10.1210/jc.2012-1444

  3. The NIH National Heart, Lung and Blood Institute. Low-Calorie, Lower Fat Alternative Foods.

Additional Reading
  • Hall KD, Sacks G, Chandramohan D, Chow CC, Wang YC, Gortmaker SL, Swinburn BA. Quantification of the effect of energy imbalance on bodyweight. Lancet. 2011 Aug 27;378(9793):826-37.

By Vincent Iannelli, MD
 Vincent Iannelli, MD, is a board-certified pediatrician and fellow of the American Academy of Pediatrics. Dr. Iannelli has cared for children for more than 20 years.