Low-Carb Diets: Changes in Weight, Mood, and Metabolism

When you’re setting out to make changes to your diet in hopes of improving your health, it’s important to remember that everyone’s experience will be different—especially if your goal is to lose weight. One change you might be considering is committing to a low-carb diet.

When you start out, you may have high expectations—especially if you’ve seen the change work well for others. Remember: Your experience may not be the same as someone else’s, even if you do all the same things, because your body is unique.

Approach your goal, be it weight loss or improved overall health, as an interested and careful observer of your body. Notice and note how your body responds to the changes you make. And while you can’t predict the exact outcome of your efforts, there are a few common experiences people can expect on a low-carb diet.

The best way to prepare yourself to cope with the challenges of a low-carb diet is to understand what happens in your body when you make lifestyle changes. Then, you can empower yourself with everything you need to confront these challenges effectively as you work toward your goals.

When you begin to change how much you eat and move, changes to your metabolism will be reflected by more than weight loss because your metabolism does more than influence body composition.

The biochemical process is constantly regulating various bodily functions like temperature, hormones, and blood glucose levels. Your metabolism does some of this work when you’re not doing much at all, like when you're resting or asleep.

There are a lot of individual factors that influence metabolism. Everyone’s metabolic rate is different and in fact, your metabolic rate will change throughout your life. Metabolism is affected by sex, age, conditions like pregnancy, illness, injury, and medications.

When you make certain changes to your lifestyle, such as exercising more and eating less, your metabolism will respond in a number of ways—some of which won’t necessarily show up when you step on the scale.

On example is how your body handles glucose. According to the American Association of Clinical Endocrinologists, impaired glucose tolerance often shows up as a fasting blood glucose measure above 89 mg/dl. This may be a sign of a metabolic condition like type 2 diabetes.

If you have any other indicators of metabolic syndrome, making changes to your diet and activity level can reduce or even eliminate signs and symptoms such as:

• Elevated blood glucose
• High blood pressure (hypertension)
• High waist to hip ratio
• High blood triglycerides
• Low HDL cholesterol

If you’re on a very low-carb diet (under 50 grams of carbohydrate per day), these changes may show up fairly quickly once your body adapts to using fat for energy instead of glucose from carbohydrates—a state called ketosis.

How much weight loss you’ll lose depends on many different factors, such as your individual metabolism and unique weight loss situation.

For example, if you’re starting out at a higher weight, you may experience more weight loss at the outset compared to someone who is not overweight. However, regardless of starting weight, the rate of weight loss stabilizes for most people after the first month.

Once your body begins to adapt, you’ll likely continue to lose weight at a stable rate for the next few months. However, at some point, it’s common for the rate to begin to slow down—and your weight loss may even come to a complete halt.

A weight loss plateau that lasts a week or two probably doesn’t represent a problem. However, if your weight loss stops for a month or longer, it may be time to take a closer look at your plan and assess how well you're following it.

In some cases, the reason may not be something you can control. For example, people with regular menstrual cycles often experience normal weight fluctuations at various points throughout the month, especially during the premenstrual period.

Another factor is your individual metabolism. Your rate of weight loss will likely slow down as time goes on due to your metabolism adjusting. That means even though you’re eating the same as you have been since starting your plan, you won’t get the same results.

One step you can take is adding or changing up an exercise program. However, our activity level is also influenced by our normal, non-exercise, movement throughout the day—what’s known as non-exercise activity thermogenesis (NEAT).

If you feel daunted by the thought of committing to a workout, start by making small changes to your daily activities first. Try making an effort to stand up when you’re talking on the phone or take the stairs instead of the elevator. 

Whenever you make a change to your lifestyle, particularly what you eat, how much you eat, and your activity levels, you can expect your mood to change as well. You may be excited, overwhelmed, frustrated, and even a little anxious.

Specific to low-carb diets, though, there are certain mood symptoms you'll want to prepare yourself for. Some people experience "lows" in mood, irritability, or brain fog when they first start reducing carbs. Your brain is used to using carbs for energy and may need some time to adjust just like the rest of your body.

Some of the symptoms people experience when they start a low-carb diet can be emotional and linked to feelings of missing favorite or "comfort" foods. These emotional responses may have physical symptoms as well, such as tension or even jitteriness. This is sometimes referred to as "carb withdrawal."

The good news is that most people find that any initial changes in mood start to improve after the first couple of weeks on a low-carb diet. As with any major change, the best thing you can do to stay motivated as seek support. Whether it be from friends and family, online or in-person support groups, or a health coach, talking through your experiences with others can help.

It’s OK if you don’t find the best plan for your body on the first try. It’s OK to completely start over, but make sure you’ve given your original plan a chance to work. Don’t let feelings of frustration and impatience convince you your plan isn’t working—while this may prove to be the case, it’s also possible you just haven’t given yourself and your body enough time.

While these intense feelings can crop up at any time from two weeks to one year into your plan, psychologists have found most people experience these emotions about three to four months into a behavioral change.

These feelings can also be triggered by a life event that changes your routine. For example, a new job, going on vacation and experiencing an illness or injury can influence your eating and activity patterns in major ways.

These changes may not necessarily be abrupt, though. You may find that as time goes on, you slip back into your old habits—a tendency that may happen without you being consciously aware of it. This unconscious slip is normal and expected, but you should take it as a sign that you need to check-in with your body and your mind.

Reflect on how you’re feeling physically and emotionally. Try asking yourself some questions such as:

• Am I still feeling motivated?
• Have I been seeing progress?
• Are the benefits worth the losses?
• Does my original goal still matter to me? Do I need a new goal?
• Do I keep hitting the same roadblocks?
• Have I discovered plenty of healthy foods I enjoy? Is my pantry stocked with low-carb snacks?
• Do I have the support I need?

While there’s no secret to ensuring long term success, the way in which you think about the changes you’re making can make a big difference in terms of how you feel about them. If you frame low-carb eating as a diet, it can feel like a temporary measure you’re only taking to reach a specific goal, such as losing a few pounds. Instead, try thinking about the changes you’re making as a long-term strategy for lifelong health.