First learning weightlifting from her older cousins, Diaz initially lifted using makeshift barbells made of mag wheels or concrete. Prior to high school, Diaz joined the University of Zamboanga's (UZ) extension program to train in weightlifting under her cousin Catalino Diaz who was also her first coach. Elementary students not enrolled in UZ were able to train under the program of Institute of Human Kinetics director Elbert Atilano. She had to do part-time work to fund her transportation to a local gymnasium. Her part-time jobs were selling vegetables and fish and washing jeepneys. Diaz's first competition was the 2002
Batang Pinoy in
Puerto Princesa. She went on to compete in various local and national competitions and secured support from the local government. Diaz became part of the Philippine national weightlifting team at age 13. This made her the first female weightlifter to compete for the Philippines in the Olympics, and the sixth weightlifter overall (the first being Rodrigo del Rosario competing in 1948 London Olympics). Competing in the
women's 58-kg class, 17-year-old Diaz lifted 85-kg in the
snatch and 107-kg in the
clean and jerk for a 192-kg total, breaking the Philippine record that she herself set at the
2007 Southeast Asian Games. Although she placed second to last in a field of 12 weightlifters, her performance was praised and considered promising for her age.
Philippine Sports Commission Chairman William Ramirez once commented that she competed there to gain valuable experience and predicted that she would be a strong contender in future competitions.
2012 Summer Olympics Diaz became the first Filipina weightlifter to compete in two consecutive Olympics, by qualifying in the
women's weightlifting under 58 kg through the Continental and World Qualifying Tournaments. She was ranked ninth in her event heading to the Olympics. During the
2012 London Olympics, Diaz was chosen to be the flagbearer during the Opening Ceremony. She was coached by Tony Agustin, and they projected a 225 kg lift, above her personal best of 219 kg. She successfully lifted a personal best of 97 kg in the snatch, 12th best among the 19 competitors. However her 118 kg clean and jerk was unsuccessful after three attempts. She was one of two competitors (along with
Lina Rivas of
Colombia) to end with an official result of "Did not finish" (DNF) in the event.
2015 to 2016 season and Nestor Colonia being recognized by Zamboanga City Mayor Mayor Beng Climaco for their performance in the 2015 Asian Weightlifting Championships in Phuket, Thailand Diaz weighed around 56.28 kg during her first Olympic campaign, making her the lightest among competitors. Come the 2012 Olympics, she had increased her weight to 57.70 kg but still struggled making it to the top half of the competition. Trying to improve her chances of landing a podium finish at the
2016 Rio Olympics, Diaz decided to drop weight from under 58 kg to under 53 kg. This proved to be effective as she won the gold medal in the 1st Southeast Asian Weightlifting Championship in Bangkok. In that competition, she managed to lift a 98 kg snatch and a 115 kg clean and jerk for a 213 kg total. The same mark was also good for 4th place later on in the 2012 London Olympics. In the Asian Weightlifting Championships, Diaz won both a gold medal in 2015 and a bronze medal in 2016. In March 2016, Diaz dominated the women's 58 kg event of the
2015-16 Philippine National Games National Finals held at Lingayen Town Plaza,
Lingayen, Pangasinan, with a 92 kg snatch and 120 kg clean and jerk (new personal best) combined into 212 kg.
2016 Summer Olympics In the
2016 Summer Olympics in
Rio de Janeiro, Diaz competed in her 3rd consecutive Olympics in the
women's 53kg weightlifting category with the intention of at least winning a bronze medal. Diaz surpassed her own personal target and won the silver medal at the event, after successfully clinching a lift of 88 kg in her second attempt in snatch event (placed 6th) and 111 kg and 112 kg in the first and second attempts in the clean and jerk event (placed 2nd). This was the first medal for the Philippines in the Summer Olympics after 20 years. This was also the first non-boxing medal for the nation since
1936. Aside from being the first Filipina weightlifter to compete in three consecutive Olympics, she also became the first Filipino woman and the second person from Zamboanga and Mindanao to win an Olympic medal (after Simeon Toribio, bronze medal winner of men's high jump in the 1932 Los Angeles Olympic Games). On August 8, 2016, she returned to her hometown, Zamboanga City and was welcomed as a hero of the city. From receiving numerous incentives from the Philippine president,
Philippine Sports Commission and her local city, she was able to buy land for her sibling and for her gym. Two months prior to the Asian Games, she recruited Gao Kaowen who was previously coach of the Chinese national women's army team. In the women's 53 kg in the 2018 Asian Games, Diaz had a total lift of 207 kg, beating
Turkmenistan's
Kristina Shermetova (206 kg) and
Thailand's
Surodchana Khambao (201 kg) to deliver the Philippines' first gold in the 2018 games, as well as being the first Filipino weightlifter of any gender to win a gold medal in the
Asian Games.
2019–20 season After winning a bronze in the 2017 World Championships, Diaz again won a bronze in the 2019 edition of the same event. She also won a silver in the 2019 Asian Championship, and another gold in the 2019 Southeast Asian Games in Manila.
2020 Summer Olympics On July 26, 2021, Diaz won a gold medal at the
2020 Summer Olympics in Tokyo. This was the first ever gold medal won by a Filipino athlete since the country's first appearance in the Olympics in 1924. She set new Olympic weightlifting records by lifting 127 kg in the clean and jerk and lifting a total weight of 224 kg. Diaz's achievements at the 2020 Summer Olympics were impressive, as she was previously stranded in
Malaysia from February 2020 until July 2021, due to
travel restrictions imposed by governments to contain the
COVID-19 pandemic. Based on guidance by her coach, Gao Kaiwen, Diaz initially went to train in Malaysia in February 2020 because Gao thought it would be better for her as she focused on qualifying for Tokyo. However, once Malaysia implemented
its Movement Control Order in April 2020, which closed gyms within the capital region of
Kuala Lumpur (
Klang Valley), she improvised by using bamboo sticks and large water bottles as makeshift weightlifting equipment. In October 2020, she relocated to the southern coastal state of
Malacca where they had been living in a house owned by a Malaysian weightlifting official in
Jasin. The Malaysian government then implemented periodic restrictions on gyms and sporting activities within 2021 (to reduce social interaction and contain the spread of the coronavirus), forcing her to work out in the house's sweltering open-air carport in the immediate months prior to the 2020 Summer Olympics. Diaz also struggled with her mental health during this ordeal, especially with the postponement of the 2020 Olympics, and credited her team, including sports psychologist Dr. Karen Katrina Trinidad and Project: Steady with trauma therapist
Gang Badoy Capati for her well-being. She also kept busy during her training overseas during COVID-19 lockdown by cooking, attending meetings, and studying. In recognition of winning the first gold medal for the Philippines at any Olympic Games, she was awarded PHP 35.5 million (approximately US$660,000) along with a house and a lot. The financial and asset awards, were jointly given by both the national government and tycoons from the private sector. Under Philippine law, the
Philippine Sports Commission guarantees a 10 million-peso incentive for every Olympic gold medal per
Republic Act 10699.
2022–23 season On May 20, 2022, Diaz won her second gold medal win during the
31st Southeast Asian Games. In December of that year, she won the gold medal in the
women's 55kg event at the
World Weightlifting Championships held in Bogotá, Colombia. In that same month, she was also elected as member of the
IWF Athletes' Commission. Diaz would move up to the -59 kg weight class after the -53 kg and -55 kg classes were not included in the weightlifting program for the
2024 Summer Olympics in Paris. She made her competitive debut in the 59kg division at the
2023 Asian Weightlifting Championships in South Korea. She placed 4th by lifting a total of 221 kg.
Hiatus in 2024 and return in 2025 Diaz failed to qualify for the
2024 Summer Olympics in
Paris after failing to finish among the top ten in the
IWF Olympic Qualification Ranking and was beaten by fellow Filipino
Elreen Ando in the 59 kg class following the conclusion of the
IWF World Cup in Thailand. In December 2024, Diaz has considered attempting to qualify for the
2028 Summer Olympics in Los Angeles. Diaz juggled training and coaching other weightlifters while preparing for her competitive return through the
2025 SEA Games in
Thailand. She placed fourth in the 58 kg class and missed the podium stating that mental preparation was her biggest issue. Despite the results, Diaz stated she is not yet retiring. In the women's 58th kg event at the 33rd SEA Games in Chonburi, Thailand on 14 of December 2025, Diaz lifted 90kgs in the snatch and 110 kg in the clean and jerk for a total of 200 kgs, finishing fourth behind Thailand (gold), Indonesia (silver), and Vietname (bronze). She described the challenge as primarily mental after nearly two years away from competition and stated, "This is my best for now" and "I'm definitely not retiring, but I'm almost there." Diaz indicated she would target the 61 kg class and Olympic qualifiers in 2026 with the goal of competing at the 2028 Los Angeles Games.
Major results ==Military career==