6 Factors that Affect Weight Loss

Sometimes it seems like everyone is on a diet. More than half of American adults report that they want to lose weight — and yet 69 percent of us remain overweight or obese.

One key reason that so many of our efforts fail: What works for one person often does not work for another.

Each of us has a unique set of factors — our own metabolism, microbiome, hormone balance, nutritional status, genetic makeup, and exposure to environmental toxins — that play essential roles in weight loss. Lifestyle factors like diet, exercise, self-care, sleep, and stress management can all interact with those variables.

“This makes one-size-fits-all plans — even the most scientifically sound ones — tricky,” says Shilpa Saxena, MD, a Florida-based physician and clinical faculty member of the Institute for Functional Medicine. “I’ve learned from experience that a diet that helps one person thrive can set another person back. Luckily, we now have the means to dig deeper for what works.”

Today, there are a host of new blood, saliva, urine, and fecal tests — available in clinics and some better health clubs — that can reveal the unique inner workings of our bodies. And there are a growing number of progressive health practitioners who can leverage the latest scientific research, lab tests, and your health history to develop a more personalized approach.

The future of weight loss is indeed customized and individualized. But tailor-made health plans are not quick fixes. The complexity of your body means that individualized plans call for detective work, experimentation, and patience.

In some ways, individualized plans can pose a greater challenge, at least upfront, than cookie-cutter plans. They require an in-depth knowledge and understanding of your unique biological and lifestyle factors, and how those influence and play off each other.

But the payoff — successful, lasting weight loss and the reclamation of health and vitality — is worth the effort of working with, not against, your body.

“Rather than force you to do something that is not in your nature, an individualized approach will allow for a unique, changing path,” says Jade Teta, ND, an integrative physician in North Carolina and coauthor of Lose Weight Here. “If you’re doing everything right and not getting results, then you’re not doing everything right for you.”

Here are the top variables that influence your ability to lose weight and how they might shape your personal plan.

1. Nutrition

Nutrition is perhaps the primary environmental trigger for weight loss and gain — but not for the reason many people think.

“Good nutrition is about more than just calories,” says Aviva Romm, MD, a Massachusetts-based functional and integrative specialist. “Nutrition — what you eat and what you absorb — acts on your genes, your hormones, your gut,” all of which affect your metabolism and your ability to control your weight.

The standard American diet (SAD) is calorie-rich and nutrient-poor, she notes, creating a scenario where many people are simultaneously overweight and malnourished. Meanwhile, many weight-loss diets are imbalanced, nutrient-poor, or at odds with individual needs, contributing to deficiencies that can interfere with the body’s ability to drop excess weight.

“Nutrient deficiencies are rampant, and they can make or break your weight-loss efforts.”

“Nutrient deficiencies are rampant, and they can make or break your weight-loss efforts,” agrees Cindi Lockhart, RD, LD, nutrition program manager at Life Time’s Twin Cities–based Proactive Care Clinic.

Lockhart recommends testing for nutritional shortcomings and working with a professional to determine what dietary changes and supplements are needed. She notes that supplements can be beneficial for filling in dietary gaps but do not replace eating healthy, whole foods.

Food sensitivities and intolerances to allergens like gluten and dairy are factors that fuel bodywide inflammation and undermine our absorption of micronutrients, both of which make it more difficult to lose weight.

Why It Matters: Deficiencies of both macro and micronutrients can disrupt metabolic pathways, reducing your resting metabolism and limiting your energy output and activity level. An allergy or intolerance can disturb gut health and create systemwide inflammation. As a result, your body may hold on to water, fat, and fecal weight.

Informative Lab Test: Full nutrition panels such as NutrEval, offered by Genova Diagnostics, run about $700–$1,200. A fecal test, like GI Effects by Genova ($450–$525), can reveal where your digestion may be limiting nutritional assimilation. Some labs may be covered by your insurance plan.

Action Plan: Try a monthlong elimination diet rich in whole foods (for a detailed program, see “The Institute for Functional Medicine’s Elimination Diet Comprehensive Guide and Food Plan“). Take a high-quality multivitamin and essential fatty acid supplement. If you don’t see improvement, consider lab testing and a personalized supplementation strategy. Genetic testing can reveal common variations that may affect your need for additional or specialized supplements (see page 39 for more).

2. Metabolism

People often complain that they have a “slow metabolism.” But thinking about metabolism in simple terms of “fast” or “slow” is a vast oversimplification of a central and complex system — one that plays a critical role in determining not just your body composition but also your overall health and vitality.

Your metabolism is a combination of all the chemical reactions in your body that keep you alive and healthy. This includes how your body uses proteins for building muscle (a process called anabolism) and how it breaks down macronutrients to use as fuel (known as catabolism).

If the catabolic aspects of your metabolism are producing more energy than the anabolic aspects require, your body will store excess fat or glycogen. You will also tend to break down your body faster than it can repair damage. This can dramatically limit your fitness results.

An active metabolic assessment — which includes a respiration test — offers a snapshot of your metabolic status, telling you how efficiently your body burns fat for energy at various levels of exertion. Some tests may also relay your VO2-max score, the maximum amount of oxygen your body can use under exertion, a helpful number in designing a personalized fitness program.

The metabolic-assessment results can tell you not only if you predominantly burn fat or carbs for fuel, but also at which heart-rate zone you switch from burning fat (the preferred fuel source for weight loss) to carbs.

“I’ve had many patients, especially women, who lost more weight by not trying quite so hard. That might mean eating a little more, exercising less intensely, and going for relaxing walks. From there, the body can start to heal itself.”

Such tests, offered at many clinics and health clubs, can also provide insight into your body’s stress level and resiliency (your ability to handle and recover from stress), and can guide both exercise and dietary shifts.

While the tests are useful tools for determining a baseline and tracking progress, you can also learn to read your own body for signs of “metabolic overstress” — red flags that your body is in catabolic mode, says Teta. Be alert for hunger, cravings, low energy, anxiety, depression, digestive disorders, hormone dysfunction, and signs of a reduced or overactive immune system.

Because eating too little and exercising too much are both metabolic stressors that can inhibit weight loss, Teta says that with overtaxed, undernourished people, dialing back grueling exercise may actually help rebuild metabolism: “I’ve had many patients, especially women, who lost more weight by not trying quite so hard,” he says. “That might mean eating a little more, exercising less intensely, and going for relaxing walks. From there, the body can start to heal itself.”

Why It Matters: Knowing more about your body’s current metabolic state can help you design a precise fitness and recovery program that maximizes fat loss while minimizing wear and tear. It can also help you shape your nutrition regimen for optimal weight loss and energy.

Informative Lab Test: Resting and active metabolic assessments (about $130), as well as heart-rate variability (HRV) tests, can guide nutrition and fitness-program design. A variety of blood, urine, and saliva tests ($148–$270 for an energy and metabolism assessment at Life Time Fitness) can offer more precise information about metabolic disruptions and imbalances.

Action Plan: Adjust your fitness and nutritional regimens to maximize your metabolic potential based on observable red flags or lab results. Give yourself time to rest and recover.

3. Microbiome

Inside of you reside some 100 trillion bacteria, yeasts, and fungi. This collection of organisms — your microbiome — influences myriad processes in your body, including fat burning and storage.

Bacteria in your gut modulates weight and metabolism by extracting energy and calories from the food you eat. In fact, people with healthy microbiomes may host gut flora that “eat” more than half their daily calories, aiding in weight loss and maintenance. On the other hand, insufficient or imbalanced bacteria can lead to weight gain.

“When we consume foods or medicines that throw this inner world out of balance, we put ourselves at risk for a host of diseases . . . . And we accumulate body fat, especially around the abdomen, gaining weight that is virtually impossible to lose,” writes Raphael Kellman, MD, in his book The Microbiome Diet.

Antibiotics, poor nutrition, and environmental toxins can damage the microbiome. Infrequent bowel movements, bloating, stomach aches, puffiness — even being overweight — are all symptoms that something is off.

Two classes of gut bacteria that are thought to especially influence body composition are firmicutes (the so-called fat bacteria) and bacteroidetes (the “lean bacteria”).

Studies show that a high ratio of firmicutes to bacteroidetes correlates to a greater adiposity index, or more body fat. But any unhealthy imbalance in the microbiome can dramatically influence metabolism and vitality, and inhibit weight-loss efforts.

Why It Matters: The balance of gut bacteria can create significant shifts in caloric energy use and storage, as well as nutritional assimilation. Moreover, the health of your micro-biome can affect your brain and, with it, food cravings. (Learn more at “Healthy Gut, Healthy Brain“.)

Informative Lab Test: Fecal tests, such as UBiome’s at-home Gut Kit ($89), or GI Effects by Genova, can detail your microbiota balance.

Action Plan: After tests reveal which of your bacteria need support, you can choose targeted food and probiotic supplements, or work with a nutritionist for pro advice. To support the bacteroidetes in your gut, eat high-quality, high-fiber carbohydrates such as leafy greens and root vegetables, tubers, and beans; avoid the processed carbs and sugars on which firmicutes thrive. Eat plenty of fermented foods and probiotics. (Bacteria with antiobesity properties include Bifidobacterium and Akkermansia muciniphila — but it’s important to tailor your supplementation to the needs of your unique gut flora.) Finally, moderate stress and get sufficient sleep: Both influence the gut environment.

4. Hormones

You produce some 50 hormones that carry messages from more than a dozen endocrine glands and signal functions in cells throughout your body. They regulate growth, sleep, hunger, metabolism, reproduction, and sexual arousal, to name a few. When any of these hormones get out of balance, it can result in weight gain or problems losing weight, says Romm.

Scientists have long hoped to discover an endocrine holy grail that causes weight gain. The closest thing to a “fat hormone” is leptin, which is produced by fat cells to tell the brain when you’re full. It works in tandem with ghrelin, a hormone that stimulates the hunger center in the brain, controlling appetite and keeping both energy and weight in check.

Excess body fat blunts the body’s response to leptin, however. The result is that ghrelin tells the brain that you have to eat while leptin never gets to deliver the signal to stop eating, even when there’s no need for extra calories.

Research shows that hormones affect more than our impulses to eat. Increasingly, physicians are looking to the adrenal and thyroid glands for clues to unexplained weight gain and weight-loss resistance.

“When someone comes in and says, ‘I’m doing everything but the weight won’t budge,’ I always look at the thyroid, adrenals, and sex hormones,” says Romm. “Is this person hypothyroid? Is this person overstressed? Are they estrogen dominant?”

The thyroid gland in your neck controls metabolism and energy, and it’s hailed as the “master gland” of your complex, interdependent endocrine system. Healthy ranges can vary widely, and fluctuation within a normal range can mean the difference between function and dysfunction for an individual. Symptoms of hypothyroidism, or underactive thyroid, include weight gain and fatigue.

The adrenal glands produce cortisol, the so-called stress hormone, which is responsible for raising your blood pressure and blood sugar and modulating your immune system. An overdose of perceived stress can cause cortisol to work against you, creating sugar cravings, anxiety, fatigue, and thyroid dysfunction, writes Alan Christianson, NMD, in his book The Adrenal Reset Diet.

Our sex hormones — primarily testosterone and estrogen — also play a role in body composition. Estrogen dominance in both genders (commonly the byproduct of too much stress, poor nutrition, and toxic exposure) can cause weight gain and other symptoms.

Why It Matters: Hormones issue the instructions that control metabolism, mood, energy, appetite, and food cravings.

Informative Lab Test: A complete hormone panel that assesses thyroid, adrenal, and gonadal hormone balance. Typical costs run $300 and may be covered by insurance.

Action Plan: Seek the advice of a knowledgeable practitioner in helping rebalance your hormones. Key steps may include dietary adjustments (moderating sugar, caffeine, and alcohol; increasing proteins and fats; eating more veggies; etc.), changing your balance of strength-to-cardio training (more strength training will optimize testosterone), limiting toxin exposure, and prioritizing recovery measures like sleep and meditation (to balance cortisol)

5. Environmental Toxins

Growing evidence shows that our modern environment — including exposure to countless toxins we don’t necessarily see, smell, or even think about — is wreaking havoc on our bodies’ ability to appropriately process, store, and let go of fat.

Nonorganic compounds (found in processed foods, cosmetics, personal-care products, dental fillings, and storage containers, to name a few) affect our appetite and metabolism, and can damage the body’s natural weight-control mechanisms.

These endocrine-disrupting chemicals (EDCs) — also called “obesogens” because they’ve been shown to encourage weight gain — include bisphenol A (BPA), often found in plastic water bottles and metal food cans; phthalates, found in some liquid soaps and adhesives; and PCBs, found in fish taken from contaminated waters.

Studies have also shown that organochlorines (OCs) like DDT (an insecticide that was banned in 1972 but continues to be detected in the food chain due to its long half-life) can promote weight gain.

A 2012 report in the journal Environmental Health Perspectives (“Obesogens: An Environmental Link to Obesity”) details a rapidly expanding body of research showing that different obesogenic compounds can have very different mechanisms of action, “some affecting the number of fat cells, others the size of fat cells, and still others the hormones that affect appetite, satiety, food preferences, and energy metabolism.”

Why It Matters: Your exposure to toxins and nonorganic compounds can alter your body’s natural weight-control mechanisms.

Informative Lab Test: Toxicity screenings, such as Toxic Effects CORE test, offered by Genova ($625–$680).

Action Plan: Since virtually all of us are carrying some level of obesogenic toxic load within our cell tissue (and especially in our fat stores), most will benefit from limiting toxic exposure and supporting our bodies’ natural detoxification processes. Lab testing can reveal the presence of particular toxins, helping to inform tailored strategies for reduced exposure and elimination. Consider an elimination diet designed to upregulate your body’s natural detoxification pathways. Vegetables such as cilantro and parsley (as well as amino-acid-containing proteins, such as eggs) are natural chelators and can aid your body in eliminating heavy metals. Aim for slow, steady fat loss and make sure your elimination is regular to rid the body of toxins that are released as you shed extra pounds.

6. Genes

Much like they have searched for a fat hormone, scientists long believed they’d someday identify a single “fat gene” — a nefarious genetic marker whose secrets, if unlocked, would help us shed unwanted pounds.

Alas, after the entire human genome of some 20,000 genes was sequenced in 2003, researchers -realized that most ailments, including obesity, cannot be clearly tied to a specific variant in a single gene.

Monogenetic obesity (in which high levels of body fat are tied to a single gene) is uncommon. It can be linked to a handful of disorders, such as Bardet-Biedl and Prader-Willi syndromes, that can result in extreme weight gain and other debilitating symptoms.

Obesity is more often the product of “complex interactions among multiple genes and environmental factors,” according to the CDC.

Obesity is more often the product of “complex interactions among multiple genes and environmental factors,” according to the CDC.

The Human Obesity Gene Map 2005, an extensive scientific review of studies that examined the genetic connection to body weight, identified some 20 genes associated with obesity; hundreds of other genes affect weight in smaller ways. In all, genetics accounts for 50 to 70 percent of weight variability.

While identifying the genes can be empowering — “Just having an answer, a reason ‘why,’ can be a huge relief and inspire someone to make healthy changes,” says Romm — the real power lies in knowing what to do with the data.

Researchers, including Christopher D. Gardner, PhD, professor of medicine and director of nutrition studies at the Stanford Prevention Research Center, are making strides in analyzing genetic markers to identify who does better on lower-carb diets and who does better on higher-carb diets, and whether genotype is better suited to eating more fats.

To some extent, genetic data is already providing us with helpful nutrition guidance. Still, many experts agree that you don’t need genetic testing to discern heritable traits toward weight gain (your family tree probably tells that story). They also point out that lifestyle factors — chiefly nutrition — powerfully influence gene expression, which can be the deciding factor in whether a genetic predisposition to obesity is ever realized.

In other words, even if you can’t dial up a diet precisely tailored to your genetic profile (yet), recognizing a genetic predisposition toward weight gain can motivate you to embrace lifestyle factors that minimize, rather than maximize, your genetic vulnerability.

Why It Matters: Certain genes can predispose you to gain weight — but individual lifestyles help determine whether those genes turn on.

Informative Lab Test: Home genetic-testing kits, available through companies like 23andMe ($99) and DNAFit ($159–$399), use saliva testing to determine whether you carry a known gene variant that predisposes you to -gaining weight.

Action Plan: You can use knowledge of your genetics — whether garnered through tests or simply from observing your family history — as an impetus to revise existing lifestyle factors (e.g., nutrition, exercise, stress, toxicity) in ways that optimize your genetic expression, switching problematic genetic factors to the “off” position as much as possible.

This article originally appeared as “Individualized Weight Loss” in the October 2015 issue of Experience Life.