Lab tests to consider on your weight loss journey

Published August 24, 2026

You’ve counted calories. You’ve shown up to the gym. You’ve started cooking more and skipping the drive-through. But the scale still isn’t moving—or not as much as you expected. Or maybe you’re in the early days of losing weight and are looking to build a plan.

Traditional advice is to eat less and move more. But achieving healthy, sustained weight loss can be more complicated. Biological factors can make it harder or easier to lose weight. Lab tests help give you insight into what’s happening inside your body. 

At questhealth.com, you can purchase a range of lab tests to help tailor your weight loss approach by better understanding what your body needs. No doctor’s visit or insurance required to purchase, and you have the ability to review your results with an independent healthcare provider.

Understanding factors that affect weight loss

Whether you’re looking to lose a few pounds or aiming to improve health measures with significant weight loss, factors beyond food and movement can affect your progress. Carrying extra pounds raises the risk of serious health conditions including heart disease, type 2 diabetes, high blood pressure, and some cancers.¹

Certain medical conditions can cause weight gain or make it harder to lose weight. Some of the most common factors that can work against weight loss include

• Metabolic syndrome
• Insulin resistance
• Hormone fluctuations
• Nutrient deficiencies

All these factors can be measured and monitored with lab tests available at questhealth.com. When they’re identified and addressed, you’re likely to see more success.

How metabolic health influences weight

You probably hear about metabolism a lot, from doctors, ads, trainers, social media influencers, and others. Metabolism refers to the processes your body uses to convert food into energy, regulate blood sugar, and manage fat storage.  

Metabolic syndrome is a group of conditions that includes high blood sugar, high blood pressure, excess belly fat, and high cholesterol. Together they raise the risk of heart disease, stroke, and type 2 diabetes. About 1 in 3 adults in the United States has metabolic syndrome.²

Carrying extra weight is both a cause and a result of metabolic syndrome. When excess weight or obesity is combined with metabolic syndrome, it can create a cycle that makes it harder to lose weight, despite your best efforts.²

Understanding insulin resistance

Insulin is a hormone produced by the pancreas that helps your cells absorb glucose from the bloodstream and use it for energy. Insulin resistance means your cells don’t respond as well to insulin. Over time, your body starts to make more of the hormone, causing your blood sugar to rise. As your blood sugar rises, your liver sends a message to your body to store excess sugar as fat.³

Insulin resistance is reversible with lifestyle changes. Knowing whether you have insulin resistance can help you tailor an eating plan that aims to maintain your blood sugar levels throughout the day.

The role of hormones and weight

Hormones regulate nearly every process in your body, including hunger, metabolism, fat storage, and energy. If your hormones get out of balance, you may gain weight and struggle to lose it. 

The thyroid gland, a small butterfly-shaped gland in your neck, produces hormones that govern the speed of your metabolism. When the thyroid is underactive (hypothyroidism), metabolism slows significantly. Weight gain may follow even without a change in eating habits, and weight loss becomes difficult.⁴

In addition to your thyroid hormones, other hormones can also play a role in your weight loss journey. Cortisol is your primary stress hormone. It increases when you’re stressed. High cortisol levels can promote fat storage around your midsection.⁵

Leptin tells your brain when you’ve had enough to eat to help you maintain your weight. However, leptin levels are influenced by body fat. The more body fat you have, the higher your leptin levels. With high levels you can develop leptin resistance. As you lose weight, your levels can decrease. In both cases, your brain may think you need more food and cause you to feel hungry.⁶

Nutrients and your weight

Even if you’re eating well, you might be low on key nutrients that your body needs. Deficiencies in certain vitamins and minerals are common. They can cause tiredness, weakness, brain fog, dizziness, or other symptoms that can lower your motivation to stick to your plan.⁷

Some nutrients to pay attention to include

• Vitamin D is produced by the skin in response to sunlight. Many people don’t get enough of this vitamin. It supports bone health and your immune system.⁸ Check your levels with the Quest Vitamin D Test
• Vitamin B12 is important for energy and focus. Low levels can lead to fatigue, weakness, and brain fog. Symptoms can undermine the physical and mental effort needed to stay consistent with a weight loss plan.⁷ Quest Vitamin B12 Test measures vitamin B12 levels to screen for deficiency
• Iron is essential for carrying oxygen through the blood to your muscles and organs. When iron is low, oxygen delivery is impaired, leaving you feeling persistently tired and limiting your endurance during physical activity.⁷ The Quest Iron, TIBC & Ferritin Panel can assess aspects of iron metabolism in your body

Developing a sustainable plan

An important part of any weight loss plan is to set reasonable goals and be patient. Weight loss can be a long journey with ups and downs. Some days the scale doesn’t reflect how hard you’re working. But meaningful health improvements happen throughout your journey. Losing even 5% to 10% of your body weight may improve blood pressure, cholesterol, and blood sugar levels.⁹

You may feel stronger, lower your blood pressure, sleep better, have more energy with family and friends, or notice other positive changes. Lab tests throughout your journey can also show your progress. Follow-up tests can help you see how your metabolic health, hormone balance, or nutrient levels are changing over time.