I Ate an Old-School Low-Fat Diet for a Week—Here’s What Happened

Updated: May 07, 2024

Oh, '80s and '90s nostalgia: A doctor dishes on the highs and lows of seven days following a low-fat diet—and defines what healthy fat intake means today.

Are you feeling the weight of holiday indulgence, just like I was? The post-festivities period often leaves many of us yearning for a dietary reset. Take, for instance, my own experience: The irresistible traditional nut roll, a staple at holiday celebrations in my hometown in Pennsylvania, seemed to cling not just to my taste buds but also to my waistline. The combination of hearty holiday meals and the sluggish aftermath of a seasonal virus had my body practically begging for an extreme makeover of the nutritional variety.

With the arrival of the New Year, our editorial team was looking for a volunteer to step back in time and experiment with a low-fat diet for a week. It’s important to note that as a trained family doctor who gained certification in nutrition coaching and diabetes prevention, and having been raised in a family of healthcare professionals, I’m usually not one for strict dieting. My typical food philosophy involves focusing on whole foods, avoiding saturated fat and trans fats, and minimizing my intake of processed foods.

Still, I volunteered. I’m a child of the ’90s, but even so, I wasn’t too keen to stock up on the diet snack cookies, low-fat cereals or margarine that were characteristic of that era (“low-fat” or “fat-free” products often contain undesirable additives and other chemicals to compensate for the lack of fat and add flavor). I also didn’t want to cut healthy fats I love, like avocados and nut butters, or healthy carbohydrates. Instead, I would monitor the healthy fats in my diet closer than I usually do.

According to the World Health Organization’s 2023 guidelines, we follow a healthy diet by balancing the amount, and the type, of fats in our diet. They recommend that adults limit their total fat intake to below 30% of their total energy, prioritizing unsaturated fats while keeping saturated fats under 10% and trans fats below 1%. (Below, we calculate this for standard American diets.) This means implementing practices such as reading nutrition labels; choosing foods like olive oil, fish, avocados, nuts and seeds; and a cautious approach toward processed foods, butter, dairy products and fatty meats.

With my background in family medicine and nutrition certification, my mission was clear: To detox my body from the holiday overload, I aimed to substitute the season’s saturated fats with healthier fats, whole grains, and plenty of fruits and vegetables.

What is a low-fat diet?

What does a “low-fat” diet really entail? Alexis Supan, MPH, RD, a registered dietitian at the Cleveland Clinic, defines a low-fat diet as one where dietary fat constitutes 30% or less of your total caloric intake.

For someone consuming 1,500 calories a day, this means keeping fat intake to 50 grams or below (with saturated fats under 17 grams and trans fats south of two grams), and for a 2,000-calorie diet, it’s about 67 grams of fat per day or less, with 22 grams or less as saturated fat and trans fats still super close to two grams.

Supan speaks to the historical popularity of low-fat diets, highlighting their reputation for heart health benefits and effectiveness in weight management. “Low-fat diets have also been promoted as a smart way to lose weight, as fat is the most calorie-dense macronutrient providing nine calories per gram, compared to the four calories provided per gram of carbohydrate and protein,” she explains.

By limiting overall fat, you naturally reduce your intake of saturated and trans fats, linked to inflammation, insulin resistance, and increased levels of bad cholesterol. Yet, it’s essential to tread carefully, as this restriction can also affect the intake of beneficial fats, like polyunsaturated and monounsaturated fats, which are known for their heart-protective properties, benefits against diabetes, positive impact on brain health, and lowering inflammation in the body.

In their April 2023 statement in the journal Circulation, the American Heart Association emphasized the concept of nutrition. They noted that while Mediterranean, DASH, pescatarian, and vegetarian diets are preferred for heart health, low-fat diets are considered second-tier recommendations. This is primarily due to their generalized approach to fats and the risk of replacing fats with less healthy carbohydrates (think white bread, white pasta, and processed food items like candy). So again, a low-fat diet could inadvertently lead to insufficient intake of beneficial fats.

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Eating a low-fat diet for a week

The first step was prioritizing a menu that was both nourishing and satisfying, while keeping my fat intake to no more than 30% of what I ate and focusing on those healthy fats. I also aimed for simplicity in my meals to avoid feeling overwhelmed. Here’s a glimpse into what that looked like:

  • Breakfast: I leaned toward low-fat staples like egg whites and oatmeal with fresh berries for breakfast. Protein smoothies became a go-to for their ease and nutrient-rich profile. When my appetite demanded more, I opted for hearty, whole-grain toast topped with avocado or peanut butter and banana slices.
  • Lunches and dinners featured various vegetables—tomatoes, cucumbers, carrots, olives—and protein sources like chickpeas and quinoa, often in vibrant, filling salads.
  • Snack times were for enjoying hummus with crunchy vegetables and Greek yogurt, occasionally sprinkled with nuts for extra texture. Lunches often involved wraps filled with an assortment of veggies and lean proteins. For a comforting and nourishing choice, I turned to homemade lentil soup, a household favorite that offered plenty of leftovers.

Dinner plates included grilled chicken alongside rice and beans and stir-fries loaded with shrimp and vegetables, paired with brown rice for a well-rounded meal. Even pasta, often misunderstood in healthy diets, found its place in my week. I chose whole grain options, tossed in a light butternut squash sauce, always cooked al dente, and served with leafy greens for enhanced digestion.

However, the week was not without its hurdles. Balancing the diet’s requirements while satisfying my taste buds and nutritional needs posed a challenge that was enlightening and, at times, demanding.

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When I ate a low-fat diet for a week, I was hungrier…at first

I initially found myself grappling with hunger pangs, especially between meals. Despite my best efforts to stick to the diet’s guidelines, there were moments when I craved more, signaling the delicate balance needed in any dietary plan. Over-restriction can unintentionally lead to increased snacking.

Supan had addressed this, stressing the importance of fats for hunger satiety and meal satisfaction. “While some people can be very satisfied with a low-fat diet, others may find themselves unsatisfied with their foods. This dissatisfaction could lead to overeating less-than-healthy options like sugar or refined carbohydrates in search of pleasure,” she advised.

In my zeal to cut down on fats, I knew I needed to avoid going to the extreme of constant hunger or dissatisfaction. As the week unfolded, I recalibrated my strategy, reaching for snacks rich in fiber, protein, and complex carbohydrates (and not the pretzels and chips in the pantry). These included fresh fruits paired with Greek yogurt, vegetables with hummus, whole-grain toast topped with avocado, and a mix of nuts like almonds, walnuts, and pistachios. This approach helped me maintain a sense of fullness and satisfaction while staying true to the low-fat approach.

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When I ate a low-fat diet for a week, I had better digestion

While the hiatus from holiday feasts and travel undeniably contributed, the transition to a diet abundant in vegetables and high-fiber foods markedly improved my body’s ability to process and absorb nutrients.

The absence of the heavy feeling that often trails rich, fatty meals was a welcome relief. It’s worth noting that meals high in fats can be harder to digest because fats take longer to break down in the stomach, and they require more bile and enzymes from the liver and pancreas. This process can lead to a feeling of fullness and bloating.

In contrast, I felt lighter and free from the digestive discomfort that had become a norm during the holidays.

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When I ate a low-fat diet, I lost weight

As Supan explained, reducing fat intake often equates to less consumption of unhealthy, calorie-rich foods, which can naturally lead to weight loss. True to her words, by the end of the week, I observed a modest yet affirming drop in weight by one and a half pounds. This was an encouraging sign of the low-fat diet’s potential when combined with conscious eating and regular exercise.

It’s important to mention that my primary aim was not weight reduction but to nourish my body adequately while maintaining daily physical activity. The weight loss was a secondary, albeit welcome, outcome. This experience highlighted that even when not explicitly aiming for calorie reduction, a low-fat diet, mindful of nutritional quality and physical activity, can subtly influence weight and overall health.

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When I ate a low-fat diet, I experienced diet fatigue

As mentioned before, strict dieting isn’t my normal practice. For me, it often feels too limiting and hard to maintain over time. Instead, I prefer to gradually introduce healthier habits into my daily routine. This approach helps me make lasting, positive changes that support a sustainable lifestyle shift.

That said, structured diets can be incredibly effective for many, and I admire the discipline and results they can yield for those individuals.

Despite my initial hesitation, this low-fat diet experience provided valuable insights, serving as a reset button for my post-holiday eating habits. While a week isn’t sufficient to assess long-term effects fully, it acted as a gentle push and put me on track to healthier eating patterns. In my career I’ve heard from patients how so often, just getting started on a plan is the hardest part. Trying the low-fat diet just for a week helped to overcome that.

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Here’s what you can do

Reflecting on the week, the overarching message is less about strictly adhering to a low-fat diet and more about understanding healthy fat consumption—while always recognizing the need for a colorful diet that’s full of vitamins, minerals, and other nutrients. It’s essential to debunk the misconception that eating fats directly contributes to body fat. The real culprits are often excessive calorie intake and processed foods.

To achieve a healthier balance, consider the guidelines suggested by Supan and other nutrition experts: Avoid trans fats and limit saturated fats to under 10% of your daily caloric intake. This typically involves reducing foods like red meats, butter, cheese, ice cream, certain baked goods, and heavily processed items. On the flip side, aim to source at least 15% of your calories from monounsaturated fats and 5% from polyunsaturated fats, which can be found in olive oil, nuts, seeds, avocados, and fatty fish like salmon.

By focusing on these healthier fat options and moderating your overall fat intake, you stand to gain benefits and hopefully feel better. Other benefits may include improved heart health, greater satiety after meals, and an overall more enjoyable and sustainable eating experience.

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