Let's say you and a friend decide to start a get-healthy journey together. You both want to drop a few pounds, build your muscle strength and reap the energizing rewards in your work and personal life. Together, you create a game plan that maps out exercise, meal plans and strategies for resisting temptations when they inevitably come along.
A month passes, and you're ready to weigh in and track your progress. You followed the same plan, so you should see the same changes on the scale, right? Actually, it's more than likely that one of you has lost more weight than the other. What gives? Well, many things, according to experts.
Everyone's body responds differently when it comes to diet and exercise. And while this can be incredibly frustrating, understanding the various factors at play can provide clarity and guidance as you work to meet your goals.
Here, what you need to know about what's happening under your hood.
1. Your Genes Are the Biggest Factor
Can you blame your mom for your constant cravings for doughnuts? Or your dad for the way you hold your weight around your tummy? Actually, sort of!
More than anything else, our genetics play a major role in our ability to lose weight, since they provide the blueprints our bodies run on. For example, some people have genetic single nucleotide polymorphisms (SNPs), which may be associated with an increased or decreased risk of being thin, Brigid Titgemeier, RDN, LD, an integrative functional nutritionist, tells LIVESTRONG.com. This may also be associated to some extent with whether a person responds better to a higher-fat or lower-carbohydrate diet. If you're curious, a doctor can do a DNA test to identify your specific makeup.
Researchers are constantly studying this field of health, trying to identify ways people can overcome some of their genetic markers, says Titgemeier. "The future of nutrigenomics and nutrigenetics is bright. This is the science of understanding how your diet impacts your genetics — by switching on or off various gene mutations that can increase or decrease risk of disease — and how your genetics impact your targeted nutritional needs," she explains.
2. Those With More Body Fat May Drop Pounds Faster
You and your pal may have the same weight-loss goal, but chances are slim that you started from the same fat mass. What does that mean? Basically, we're talking about your bodies' muscle-to-fat ratios.
As clinical dietitian Carla Dueñas, RD, explains, a person who has more body fat will likely lose it faster than another person who is closer to their ideal body weight.
Plus, how each of you look throughout the journey will differ dramatically, depending on where you started from and the areas of your body that you target in your fitness routine. "Fat loss is seen in different parts of the body at different moments. One week it may be lost from the thighs, the next from the stomach. This is partly determined by genetics but also by which muscle we are exercising as well," Dueñas says.
"If you do not properly manage stress, it will signal your body to hold onto every calorie that you consume."
3. Stress Comes into Play
How you manage the stress in your life, from career to relationships and beyond, is another factor at work. How you process anxiety and stress triggers has an impact on how your body releases or holds onto weight, Titgemeier says.
"If you do not properly manage stress, it will signal your body to hold onto every calorie that you consume," she says. "The low-grade, chronic stress of emails, endless to-do lists and being everything to everyone else — these all put the body in fight-or-flight mode, which can increase production of stress hormones like cortisol and adrenaline and lower protective hormones."
Read more: 7 Workout Classes That Will Bust Your Stress
4. Exercise Intensity Matters
There's a difference between giving 100 percent in your spin class and barely getting through it. How intensely we exercise and how much effort we put into our fitness programs can make or break our weight loss, since all of that calorie-burning fuels our metabolism, energy and other fat-burning processes.
"Your body might respond to fitness faster than your friend if you are exercising at a higher intensity. If you're working harder and burning more calories, it's possible you will see weight loss and defined muscles sooner than someone exercising at a lower intensity," explains Annie Reed, RD.
On the other side, though, Reed notes that where we start from should be considered, too. If you went from no exercise to working out five days a week, and your friend was already exercising regularly, you may see results faster because you made a dramatic change.
Your fitness history also plays a role, says Dueñas. If you exercised regularly in the past, your muscle memory may kick into gear when you start up a routine again, making you likely to adapt to a higher-intensity program more quickly — and thus, shed weight at a faster rate, too.
5. Some People Burn More Calories at Rest
Also known as BMR, your basal metabolic rate is how much energy your body needs to function at rest. This dictates your metabolism, which is the rate at which your body processes food for fuel (aka burns calories), explains Audrey Heist, RD, director of health engagement at New Jersey's AtlantiCare healthy system.
While your BMR is somewhat determined by genetics, it's also tied to your age and how active you are each day. If you're in your 40s and your friend hasn't yet reached 30, for example, your metabolism will likely be slower, making it difficult for you to lose weight as quickly.
6. Certain Conditions and Medications Might Hinder Weight Loss
Unfortunately, there are some diseases out of our control that have a significant impact on how our body responds to diet and exercise. Diabetes is one of the major ones, Reed says, since it's a condition in which the body does not use insulin correctly. Insulin is known as the "fat-storage hormone," so this condition can make it tricky to maintain a healthy number on the scale.
"When a person with diabetes or even prediabetes has high levels of insulin in the blood, it can be very difficult to lose weight," Reed says.
And if you are working hard and seeing little results, you may want to give some thought to any medications you may be taking, since they can cause you to retain extra pounds, too. A candid chat with your doctor is a good idea if you're concerned about any potential medication side effects.
7. The Tiny Bacteria in Your Gut Can Have a Big Impact
There's a lot more happening in our stomachs and digestive tracts than most of us realize. In fact, Titgemeier says the large intestine alone includes trillions (yep, you read that right!) of bacteria, fungi and other organisms. Collectively, this is known as your gut microbiome.
"Research shows that the bacteria in your gut microbiome controls your metabolism of drugs and absorption of nutrients, directs two-thirds of your immune system and also plays a role in a person's weight," Titgemeier says.
In one study, published February 2018 in Obesity, individuals who were considered obese were found to have lower levels of "good" bacteria and higher levels of "bad" bacteria in their guts. So, if you're on a mission to lose weight and you aren't giving your gut much TLC, you likely won't see as much success. "The simplest way to start is to incorporate one to two fermented foods daily. Think sauerkraut, raw apple cider vinegar, kimchi and miso, just to name a few," Titgemeier says.
Read more: 5 Probiotic-Rich Recipes Your Gut Will Love